Adaptive Immune System - Part 2

In contrary to the innate immune system I posted last time, https://steemit.com/steemstem/@tngflx/pathogen-invasion-how-your-body-protects-you

Adaptive immune system is much advance defense mechanism than innate immune system. It consists of more specialized cells that work together to combat pathogens that broke through the first line of defense (innate immune system), Adaptive immune system also provides lifelong protection by creating immunological memory after being exposed to infection (Yes your body is that amazing, it even have it's own memory). But sometimes it can mistakenly destroy harmless cell which resulted in asthma, hayfever or even allergy that we see.

SOURCES

Cells that are responsible for different type of immunity

LYMPHOCYTES

They are the cells of adaptive immunity. Lymphocytes develops from its precursor in the primary lymphoid organ thus giving its name T or B lymphocyte. It is called T-lymphocyte when it matures in the thymus, while B-lymphocyte when it matures in bone marrow. So why separate them out? Cause B-cells take on a big role in HUMORAL IMMUNE RESPONSE while T-cells are active in CELL MEDIATED IMMUNE RESPONSE. I'll talk about it more in detail . Matured lymphocytes, no matter T or B will recirculate in secondary lymphoid organ(lymph node, spleen, mucosal tissue) cause foreign particles are mostly concentrated in this region. So they have to find a mate.

CELL MEDIATED IMMUNE RESPONSE

SOURCES

• Still remember that dendritic cell I talked about in my previous post? They are the guardian of our skin cells or epithelial cells. They took in the invading pathogen from the skin and transport the antigen/parts of the bacteria and carried it to our lymphoid organs.
• Dendritic cells matures and exhibit high levels of MHC molecules and costimulators. What is MHC? MHC is Major Histocompability molecule is a receptor on dendritic cells, which is responsible for the recognition of your own cells by T-lymphocyte. So that T-lymphocyte won't attack it's own cells. That's why you see some autoimmune disease are caused by disruption on this molecule. Mostly through HLA gene (Human Leukocyte Antigen) that encodes the production of MHC molecules.
• Native T-cells recognize the MHC associated with antigen displayed on top of the dendritic cells
• T-cells is alerted and activated to proliferate and grows into effector and memory cells.
• Both T-cells migrate to the sites of infection
• Cd 4+ T-cells activate the phagocyte to engulf and ingest the microbes
• CD 8+ cells activate T-killer cells to perforate the cell wall of microbes thus leading its death.

HUMORAL MEDIATED IMMUNE RESPONSE

There are two ways B-lymphocytes get activated :

• T-cell independent - As the name implies, it doesn't need the help of T-helper cells to recognize there's an invasion. Polysaccharides or some smaller molecules left by pathogens can cross-linked with antibodies produced by B-cells thus skipping the help of T-cells.
  -T-cell dependent - Depending on T-cells to get activated. This is because larger globular protein can't bind with antibodies provided by B-cells.

As you can see, from the diagram above. B-cells produced a lot of different antibodies. Let me explain :

• Ig G : Coat microbes and presenting them to phagocytes. Phagocytes chew this microbes away to destroy it.
• Ig G and Ig M also activates the complement system. More detail about complement system
• Ig M involves in early stages of infection, while Ig G are more active in chronic stage of disease.
• Ig E helps with killing helminthic parasites for example, flatworms or tapeworms
• Ig A found in mucosal area, for example gastrointestinal lining, urinary tract. They prevent colonization of microbes.

IMMUNOLOGICAL MEMORY

Immunological memory are cells that won't die even years after the infection is cured. Your body is a revengeful person, he won't forget who invaded it before. This is to ensure if there's a second time of infection, your body will response faster and more efficient.

• If reinfection happens :
  T and B memory cells will each individually and directly differentiate to plasma cells and cytotoxic T-cells. This skips the step as I told above. From the dendritic cells that brought the antigen to the secondary lymphoid organs and wait it to be mature. This also explains why innate immune system is the first line of defense while adaptive immunity is delayed immune response. Memory B cells during this second reinfection also resulted ten to hundred folds more antibodies compare to the first infection. This result in real rapid removal of threatening pathogens.

Source : naturalnews.com

• Vaccination :
  Vaccination utilised this understanding to speed up our immune response to particular pathogen before it even stand a chance to be real virulent. Vaccination is actually injection of weakened or scientifically term attenuated pathogens. First injection to the body will stimulate the production of antibodies so it will react faster when we are exposed to the real infection.