Overview of immune system Part 3

Immune system

Adaptive immune defenses

B lymphocytes & production of antibodies

B lymphocytes

Last episode we covered the innate immune defenses and how they truly use their all power and their innate property of killing and protecting you from outer invaders, we talked about phagocytes (Neutrophils & Macrophages) how they gobble them up through phagocytosis also natural killer cells and their ability to stimulate defected and cancerous cells to initiate apoptosis ''program cell death''

Today our second defenses ''adaptive immune defenses'' these defenses show up only on one condition when the innate defenses fail to take control of your body when there is an infection. In other words, when the outer invaders are overwhelming, any antigens such as bacterium, fungus, toxins, cancerous or defected cells, what characterizes your adaptive immune defenses is that they have the ability to remember the specific antigen which invaded your body also the adaptive immune defenses are more likely to be slow to progress in your body ''adaptive'' means it needs first to identify the antigen's characteristics and properties in order to initiate its attack so it is more ''specific'' than innate immune defenses also known as acquired immune defenses.

What are the defenses of the adaptive immunity?

It has two ways of defenses:

                                             1)Humoral immunity

                                             2)Cellular defenses ( we will discuss that in the next part)

Humoral immunity means protection of the body through something called ''Antibodies'' antibody-mediated immunity existing in extracellular fluids(ECF) '' all body fluids found outside the cell'' such as blood & lymph, antibodies(=immunoglobulins)  are Y shaped little protein molecules that has the ability to block the binding sites of a particular antigen of the foreign invader, consists of heavy and light chains''

-These antibodies are produced from special immune cells named B lymphocytes, these immune cells originate in bone marrow and mature in it by learning how to recognize a foreign antigen, avoid attacking your own body's antigens ( auto-immune disease) and by dispatching more than 10,000 protein receptors (antibodies) membrane-bounded antibodies.

-Once the B lymphocytes mature they start patrolling the body's fluids such as lymph, blood and the interstitial fluids between your cells searching for any pathogens and in case it finds one which matches a particular antibody on its surface it will bind to it and they start dividing producing and differentiating into Memory cells & plasma cells ''they are special type of differentiation of B lymphocytes that preserve the threshold antibody for that specific antigen whom invaded your body'' this process is considered to be your primary immune response which will take sometime to respond and act but any further attacks that may invade your body of the same antigen will initiate the secondary immune response due to the presence of your memory cells that has the particular antibody for that antigen so it occurs much faster.

-Plasma cells are packed up with rough endoplasmic reticulum ( cell organelle studded by ribosomes molecules on its surface that's why we term it by ''rough'' functions in assembling proteins for your cells and in our case antibodies) which acts as an antibody factory, it produces the particular antibody spreading it out through your whole body fluids 2000 antibody/second for like 4 or 5 days, so we conclude that they are free-floating meaning they will be just like cells moving around till they find and bind to the foreign invader's antigen blocking them from binding to any of your cells, antibodies can fully block the sites of binding of the foreign invaders in a process called Neutralization or another way since antibody's structure have several binding sites they have the ability to bind to more than antigen of a foreign invader resulting in clumps/groups/antigen-antibody clumps in a process called Agglutination, these clumps makes it an easy target for phagocytes like macrophages to phagocytose them, this process is termed as Opsonization '' means marking or identifying the foreign invader to phagocytes, the identification is by the antibodies''

How do the phagocytes respond?
It happens that the antibodies have the ability to produce substances that attract other immune cells like phagocytes and other cells from the adaptive immune system to get to the site of infection where these bad guys are blocked to bind anything.

All that we have been discussing can be called ''Active humoral immunity'' as a definition it is when B lymphocytes mature and start to produce antibodies for the specific antigen invader, this is so important to your immunity since it increases your body's immune system efficiency and strength, the more specific antibodies for specific foreign antigens you have, the more immune you are.

Vaccination
-This is more likely to be active humoral immunity but it happens artificially without the body's own cells, a vaccine is usually a sample of the specific pathogen extremely weakened or has lost the ability to reproduce or it can't invade cells anymore which are then injected to your body, this will initiate your body's immune response to eliminate the pathogen quickly and save a copy of its characteristics & properties .e.g. the needed antibody for that specific antigen,

-Cell culture adaptation, they allow the virus to reproduce in a weak medium meaning, not human cells.e.g. they inject the virus in chicken embryos in a petri dish making the virus adapt to this type of infection (chicken embryo cells) they are then adapted to infect chicken cells since viruses reproduce a lot they then take some of the reproduced viruses and inject them into human, the virus isn't acquainted or having enough strength to reproduce and invade human cells allowing the activation of immune response to identify and get rid of the invaders while saving some other cells for any further comebacks.

Passive humoral immunity
From its name we can conclude that it is not obtained from the body's own cells, for example, babies, while they are in their development stages in their mother's womb, receives ready-made antibodies from the mother's placenta '' placenta is a sac-like organ develops from the mother's uterine wall which connects the baby to the mother through the umbilical cord, it is where the exchange of nutrients, oxygen, carbon dioxide and wastes occurs between the mother and the baby'', later on from breast milk.Unfortunately, passive humoral immunity is a temporary immunity which means the baby's own immune system won't remember any antigen it has cured of it before if it gets infected again.

Passive humoral immunity can be also obtained artificially which is usually done when the person is infected with a very serious disease which has not yet cured but some others somehow survived by receiving exogenous ( means developing or originating from outside of the organism) proteins '' antibodies'' from the plasma of other persons.

No matter what happens, somehow pathogens will find a way to get into your cells and start reproducing, this is what we are going to discuss in the next part of our overview of the immune system!

Production of antibodies

The antibodies also known as immunoglobulins are small Y shaped protein molecules that are membrane-bounded to B lymphocytes and produced from special derivatives of B lymphocytes known as plasma cells to bind to the receptors (antigens) of foreign invaders and they mainly consists of heavy & light chains connected to each other by a disulphide bridge, on the edges of these two chains there can be found the variable regions of the antibody, it is what makes each antibody different than the others while the rest are constant regions.

-Antibodies has various forms/types, the isotypes of antibodies are:
                                                                                                            1)IgM                   3)IgA
                                                                                                            2)IgD                    4)IgE
                                                                                                            5)IgG
First of all, a progenitor B cell which is a biological cell more likely to be a stem cell differentiates to B cell which has the DNA containing genes responsible for the production of these antibodies which then later produces and put them onto its membranes making it bound to it, B cells when they are later differentiated into plasma cells which produce one specific antibody.

How heavy chains forms?

-The germline DNA(=constitutional DNA, is the source of DNA for all other cells in the body) with its long strand carrying various genes on it, the first is the ''V'' region which stands for variable, this region from its name we can say it is changeable, then the ''D'' region stands for diversity, making it the remarkable region which specializes antibodies meaning that they have variation, after that the ''J'' region stands for joining, which later on join the chains with each other, last regions are M, D, G, E & A and they are the constant regions of the antibody's structure.

The V, D & J region mainly consists of 40, 25 & 6 parts respectively, pretty much,  right? That's what makes the very long number of a variety of antibodies and the big amount of them which can be produced.

The mechanism of how the heavy chains forms start by the following:

One part of each D & J region are chosen making a part of D connected to J region labeling them as DJ recombination while the V region & the constant regions connected together with the DJ recombination, after that one part of the V region leaves its friends and connect with the DJ recombination forming VDJ recombination yet the constant regions still connected to the VDJ recombination labeling this as Recombined DNA, due to the many parts present of these genes we can create many antibodies, after that the whole strand of DNA gets transcribed into mRNA strand now to the important stage which is what constant regions are made up of, the constant regions gets spliced away leaving only one of them in our example let's say it is the ''A'' region so our new piece is a VDJ regions connected with an A region naming it spliced mRNA, later on, this spliced mRNA will be translated into the proteins forming what we know as ''Antibody'' Y-shaped protein structure, the same thing happens to the formation of light chains except that there isn't a D region in its structure just directly V connected to J region.
               
                                                                      *****

References used:

http://www.cancer.gov/publications/dictionaries/cancer-terms?cdrid=561402

http://medical-dictionary.thefreedictionary.com/opsonization

http://www.healthline.com/health/placenta-previa#Overview1

https://meducation.net/

https://www.youtube.com/channel/UCX6b17PVsYBQ0ip5gyeme-Q

Antibody's isotypes

Opsonization simple explanation 

Antibody structure

Diagram showing various movements of antibodies blocking the sites of binding

                                                                                                     

Overview of Immune system Part 2

Immune system

Innate immune defenses 

The immune system isn't like the other systems in their description. In other words, the immune system is not a full/specific organ like the other systems for example when we recall the digestive system we know we are talking about the stomach, small intestines, esophagus and so on, when we say the respiratory system we know we are talking about the lungs, alveoli sacs and etc..

The immune system is the lymph nodes, vessels, tracts & trunks, also lymphocytes and bone marrow, the immune system's job is a prerequisite in order to live, the immune system helps our body keep foreign invaders outside of our bodies such as bacteria, virus, and fungi that are waiting for any chance to use you and your body's resources to divide, so our body needs to develop special soldiers in order to avoid these bad guys, for example, our first line of defense like our external barricades is our skin, the skin is made of three layers 1)epidermis *the outermost layer* 2) dermis *the inner layer* 3) Hypodermis *the deeper layer*

1)Epidermis,  several layers of epithelial cells, Stratum(corneum, lucidum, granulosm& germinativum) at the surface of this layer where the exterior cells exists are dead keratinocytes cells exists which makes up the substance of skin called Keratin, at the base of its inner layer, there are pigment cells which secrete granules responsible for the color of the skin through cells called melanocytes, the darker is your skin the more active melanin you have and vice versa.

2)Dermis, lies beneath the epidermis, consisting of connective tissues, also is crucial since it contains blood capillaries, nerve endings, lymphatics, sweat glands, fat glands, fatty cells and hair follicles, the sweat gland is one of the various points we will talk about as something related to our immune system, these sweat glands through coiled tubes that reaches the skin surface through a pore secretes sweat which mainly consists of NaCl + water, some bacteria cannot bear the acidity of such secretions our skin releases, therefore our skin has sort type of immunity to our body so we categorize it in our innate immune defenses, also the presences of some peptides called defensins 
( antimicrobial polypeptides, they invade microbes )that also provides an immunity function by attacking any bacteria or fungi by binding to their membrane and increases their membrane permeability.

The presence of mucous membranes in our body that covers all the tracts that lead to the outside world such as digestive, respiratory, urinary & reproductive systems also have an immune function, mucous mainly composed of Mucin( mucin is a family of large heavily glycosylated proteins, ''glycosylation'' as a definition means the reaction in which a carbohydrate molecules ( glycosyl donor) is attached to any functional group of another molecule ( glycosyl acceptor) it is more likely a type of covalent bonding, these molecules or membranes tends to protect you from the outside world.

For example, your nasal passages containing mucous protect you from any harmful foreign invaders (airborne vectors) that you may inhale frankly as well as the presence of cilia which work on kicking out any tiny objects such as dust.

The saliva which your salivary glands secrete mucin, salts, and lysozymes among other things help protect you from anything you may take in while eating or through a mouth breath, lysozymes also known as bacteria-fighting enzymes destroys the bacteria's cell wall.

Your lacrimal eye fluid(tears) also has an immune function, it consists of water, electrolytes such as sodium & potassium, proteins such as lysozymes, immunoglobulins ( antibodies), mucin, defensins, and lipids among other things.

Your stomach which is a main digestive organ, any type of vector that somehow made it to your stomach can be eliminated due to the presence of acids secreted by the stomach in order to digest food such as HCl, pepsin, and enzymes secreted by the pancreas that tends to break down lipids, carbohydrates and proteins also tend to help in immunity.

In case any successful vector such as Staphylococcus bacteria( gram +ve bacteria) made it to through any cut you have made accidentally while peeling an orange, this induces your internal innate immune defenses where your body tends to activate a sort of weapons that work against these foreign objects such as fever, chemical signals, and inflammation,

What happens in the case of an infection?

It is a beautiful day until you accidentally cut your skin, nearby bacteria seize the opportunity and enters through your wound starting to divide, your body's first line of defense that arrive to the scene are phagocytes such as neutrophils which are the most abundant type of your innate immune cells they range in percentage of 40 to 70% they mainly destroy the bacteria and any toxins secreted by them their nucleus has two to six lobes also they tend to commit a suicide right after destroying any foreign invaders.

Another type of phagocytes which are bigger are Macrophages meaning big eaters, they have two types, mobile and fixed, the fixed ones such as those found in the liver where they are fixed on the liver cells tissues and others are mobile which has the ability to move around, they kill bacteria by engulfing them through cytoplasmic extensions through a process called phagocytosis, where the bacteria is eaten and digested due to the presence of various and more lysosomes ( lysosome is a cell organelle found in eukaryotic cells functions in digestion and waste removal so it has enzymes) these lysosomes tends to surround the bacteria and releases its enzymes, what characterizes the macrophages unlike the neutrophils they can devour many bacteria, fungi or viruses up to 100, macrophages are derived from immune phagocytic immune cells known as monocytes comprises about 3 to 8%, these cells that has left the bloodstream.

Natural killer cells, these cells aren't phagocytic, these immune cells patrol all your body cells looking up for any infected cells that has been infected by any sort of a vector, through cell signaling by sending messenger proteins which tends to activates a process known as apoptosis '' program cell death'' induces the cell to kill itself, the way the natural killer cells identify the infected or cancerous cells is that each normal cell has a special antigen called MHC1 '' Major histocompatibility complex'' also known as human leukocyte antigen ( are group of genes that expresses proteins found on the surface of cells that help the immune cells to identify any foreign invaders) but when any normal healthy cell gets infected they lose this antigen.

So back to the cut you had when you were peeling the orange, bacteria nearby embrace the opportunity and gets through, your body innately tends to protect you from any loss or any breach from foreign invaders into your body, so your damaged skin cells that have been affected by the cut releases chemicals known as chemokines ( small protein molecules, chemo>>chemical, kines>>kinetic*movable*) which tends to inform your body that something has gone wrong then this launches inflammatory response through chemicals, redness, swelling, heat, and pain for example in your dermis skin layer exactly in the connective tissue of this layer has specialized cells called mast cells ( are cells filled with basophils granules that releases histamine molecules & other substances during allergic reactions and inflammatory responses) mast cells basically fight worms, communicate with other cells, activate cells and causes inflammation as well among other things, histamine molecules one of the main factors of causing the inflammatory response, it goes to the capillaries feeding the skin cells with oxygen & nutrients  deeper into the endothelial cells layer stimulating them to widen & separate between each other to make the capillaries larger leading to what we call vasodilation which makes you feel with enlargement or swelling, this is helpful and are actual signs of healing since it helps increase the blood flow to the damaged tissue, platelets start to clot the wound in order to prevent more blood loss, fibroblasts found in the connective tissues secrete collagen( main structural protein found in the connective tissues of animals) towards the cut to take the shape of the original worn out tissue.
Since the capillaries are vasodilated and capillaries contain blood which in our case has lymphocytes and white blood cells that pass by, they will squeeze through the separated/widened capillaries moving towards the site of infection through a process called leukocytosis it is also a sign of inflammatory response where the number of white blood cells increases in number during an infection but when the foreign invaders are overwhelming the macrophages and neutrophils releases fever-inducing substances called pyrogen ( low molecular weight protein, endogenous since it is produced from the leucocytes) in response to the exogenous pyrogen released from the bacteria (foreign invaders) released into the blood circulation which stimulates the hypothalamus.
The hypothalamus is a section of the brain responsible for the production of many essential hormones that control different organs and cells, in our case the hypothalamus among other things is responsible for temperature regulation, thirst, and hunger, so when the pyrogen chemicals are released they stimulate the hypothalamus to increase the body temperature resulting in a higher metabolism of your cells making them consume more oxygen& nutrients leading to a faster healing, also this induces the liver and spleen to hold their iron and zinc in order to prevent the contribution of these materials to the growth of these foreign invaders that's why the person infected with any bacteria or virus tends to breathe heavily, lose appetite and feels sleepy among other things.

Thanks to the following websites and youtube channels for making this overview possible and I really hope you get educated and I am hoping you give me your feedback in the comments section, Thanks a lot.
References used:
http://www.healthline.com/human-body-maps/hypothalamus
http://medical-dictionary.thefreedictionary.com/pyrogen
https://www.britannica.com/science/major-histocompatibility-complex
https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-physiology-textbook/integumentary-system-5/accessory-structures-of-the-skin-65/sweat-sudoriferous-glands-397-4497/
http://www.nature.com/eye/journal/v17/n8/fig_tab/6700566t1.html#figure-title
http://www.medicinenet.com/script/main/art.asp?articlekey=26300
https://www.youtube.com/channel/UC4a-Gbdw7vOaccHmFo40b9g  (Khan Academy)
https://www.youtube.com/channel/UCX6b17PVsYBQ0ip5gyeme-Q (CrashCourse)

Stay tuned for the next part, we will talk about some adaptive immune defenses!!

Diagram showing the existence percentage of some white blood cells in the blood

Capillary tube contents after centrifuge, discussing the presence of platelets that clots the damaged tissues, lymphocytes and white blood cells 

Capillary beds and the exchange of gases and nutrients to the damaged tissues 

Overview of the lymphatic and immune system Part1

   

LYMPHATIC SYSTEM

Lymphatic system: It is a network of vessels, organs and tissues containing lymph which is a fluid containing infection-fighting white blood cells that spreads throughout the body.

Also a part of circulatory system and plays a vital role to our immune system

Lymph is the interstitial fluid that gets absorbed when forced out of the capillary tubes.

-One function of the lymphatic system is that it maintains our body's homeostasis.

Homeostasis means balance, a way or process your body does by controlling the concentrations of substances in solution, temperature, etc.. in order to remain everything near constant level, the plasma membrane is so related to homeostasis so check out the last video below for more understanding.

Any failure to perform homeostasis may lead to life threatening consequences such as swelling ankles, lungs can be filled by fluids, the failure to control concentrations can decrease the blood pressure and volume.

Lymphatic system structure:

1-Lymph, a watery(liquid) solution which is most likely to be plasma and NOT blood; because red blood cells are big enough that they cannot squeeze out of your capillaries

Mainly consists of blood plasma which is forced out of your capillaries where the leakage helps the exchange of nutrients and gases between the blood and capillaries and the cells.

2-Lymph nodes, network of lymphatic vessels reabsorb the blood fluid (lymph) which transport them to lymph nodes which are found at certain points throughout the body, they  are more likely to be your checkpoints, they help in monitoring/cleaning/eliminating any microbes or such foreign bodies present in your lymph.

3-Lymphatic organs: a-Spleen( major lymphatic organ) found in a suitable and safe place behind the stomach and just in the front of the left lobe of your liver, spleen has various functions such as getting rid off of dead red blood cells, oxygen-rich blood reservoir and cleans the blood off foreign invaders

b-Thymus gland, a gland that exists in your neck behind the sternum in an appropiate place between your lungs, also provide a vital immunity role to your body by secreting thymosin hormone which stimulates the maturation of disease-fighting lymphocytes called T-lymphocytes

c-Adenoids

d-Tonsils

Both the spleen & thymus provides a safe place for immune cells such as T and B cells, natural killer cells, dendritic cells and R.B.Cs.

Starting from the capillaries......,

The capillaries are tiny, microscopic vessels which connects the arterioles with the venules.

Carries blood from your arterioles and feed blood into venules, their walls which are very thing consists of one row of thing epithelial cells with tiny pores between them, the wall of the capillary is about 0.001 micron thick which facilitates a quick exchange of substances between the blood and the tissue cells.

Capillaries are spread in the spaces present all over the body tissues as a wide irrigation system.

The exchange of nutrients and gases is due to osmotic pressure, it is the diffusion of solutions/substances through a semi-permeable membrane, it increases by the increase in concentration of solutes in solutions.

-About 3 liters per day  of the fluids which is about more than half of your total blood volume  that passes through the blood capillaries are picked up by the lymphatic capillaries that exists through the spaces present in the capillary vessels. Their walls consist of endothelial cells with valves that opens only in one direction, the presence of smooth muscles in the inner lining roles in moving the lymph as well as the skeletal muscles which when squeezing (contracting) increases the pressure on the lymphatic vessels and therefore, the lymph moves forward.

These walls are forced to be opened when the concentration of solutes on the outside is more than that on the inside of the lymphatic vessel. Once filled, it is then taken to various nodes and are eventually drained into two big ducts.

-The right lymphatic duct takes lymph from the upper right area of the Torso, including the right upper arm and right side of the head & thorax feeding all into the Internal Jugular Vein ( a major blood vessel that drains blood from important body organs and parts such as the brain, face and neck, they functions in carrying oxygen-depleted (less) blood from the brain, face and neck and transport it to the heart through the superior vena cava).

-The larger thoracic duct takes lymph from the rest if your body sending them into the subclavian vein.

Lymphatic vessels works under low pressure, containing valve that prevents any back flows as well as the presence of smooth muscles that help in movement and support.

Any decent exercises or movements are good enough to help keep up your lymphatic vessels.

Ultimately, the lymphatic system functions in taking extra fluids and cleans it from any microbes.

Now back to the vital role of the lymphatic system to our immune system, throughout our lives our skin which is considered to be the largest organ is surrounded by many bacteria that standing for any chance to infect your body starting from a small cut in your skin.

For example, staphylococcus bacteria (gram +ve bacteria) sneaks through your loose areolar connective tissue ( a multi-functional tissue that serves structural, adhesive, and immunological functions consists of collagenous fibers and elastic fibers )

Recall lymph nodes....?

Since they contains the checkpoints in other words, the protection against foreign bodies that wants to breach our body, it is also the place for lymphocytes exists (T & B) and where they mature in the loose reticular connective tissue that makes up a large part of the nodes and most of your other lymphoid organs.
-Lymph enters the lymph nodes through a vessel called Afferent vessel  and exits through Efferent vessel

Mucosa associated lymphoid tissues

a.k.a MALTs are also tissues that functions like our lymph nodes such as tonsils (two small masses of lymphoid tissues in the throat), Mucosa? because they are present in the mucous membrane outside the lymphatic vessels, the tonsils inspect everything that you eat, another example is peyer's patches found in the distal portion of small intestines ( consists of a group of lymph nodes) also appendix ( which happens to have lymphatic nodes & vessels)

Figures

Diagram of a lymph node showing its structure

Picture showing the structure of a lymphatic vessel

Diagram of the lymphatic vessel showing its structure and its histology

Loose reticular connective tissue diagram

Diagram showing lymph capillaries in between blood capillaries

Loose areolar connective tissue

I hope you guys enjoyed the topic today, the following videos will help you revise and understand with extra information about the lymphatic system, I don't own any of the following videos also stay tuned for more biology stuff and the next parts of this overview =) WE LIVE WE LEARN

Thanks to Tammy Moore, here is her channel https://www.youtube.com/user/armoorefam

Thanks to CrashCourse, channel's link: https://www.youtube.com/user/crashcourse

Thanks to Jenny Klemme, here is her channel: https://www.youtube.com/channel/UC1WLVcjqO44TPUnV2zvPrcQ

Thanks to Amoeba sisters, link to their channel: https://www.youtube.com/channel/UCb2GCoLSBXjmI_Qj1vk-44g

Next part will be more into the immune system deeper into it, we will discuss immune cells their functions also we will have an example to help in understanding what happens when the body is infected, it will be about bacterial infection.

What you want to know about ''Homeostasis'' is here,

A quick peek about the various body tissues we got