Cell recognition and the immune system

What is immunity? 

The ability for oraganism to resist infection by protecting themselves from disease causing microorganisms or the toxins that invade their body. 

What is a antigen?

Its any part of a organism/substance that is recognised as non-self, by the immune system and triggers a immune response. 

The Body has defence mechanisms, theres 'Specific' and 'Non-specific' types.

Specific- Cell mediated response (T-Lymphocytes) 

           -Humerol response (B-Lymphocytes)

Non-Specific- Physical barrier e.g skin 

                  -Phagocytosis 

Specific responses are less rapid, are (gosh) more specific but leave long lasting results. 

Reconising your own cells (Lymphocytes) 

You need to able to distinguish your own cells or Lymphocytes would destroy the organisms own tissues.

Each cell has specific molecules on it's surface. Proteins are one of these molecules, and are very important.Theres Enormous variety, because the highly specific teritary structure. These differences in proteins enable cells to be intentified.  

This allows the immune system to indentify;

Pathogens, non-self material, toxins, and abnormal body cells (AKA CANCER).

Transplants

This system to recognise cells has implications.

Your body finds transplants as non-self.

Therefore attempts to destroy it.

TO MINIMISE RISK

Immunosuppresent drugs and a close tissue match. 

Lymphocytes 

They are white blood cells. They are produced in the stem cells in the bone marrow. 

Two types;

B Lymphocytes; Mature in the bone marrow. Involved in the humoral response. (Humoral means body fluids)

T Lymphocytes; Mature in the Thymus. They are associated with cell mediated immunity. (involves body cells)

Lymphocytes will respond to a organisms own cells that have been infected by non-self material from the SAME SPECIES.

Why?

Because they are genetically different. Therefore there will be different antigens on it's C-S-M.

Lymphocytes can distinguish invader cells from normal ones by these cells presenting foreign antigen on their C-S-M;

Phagocytes (they engulf hydrolysed material)

Body cells invaded bya virus

Transplanted cells

Cancer cells

 How T-lymphocytes respond to infection of a pathogen;

*Pathogen invade body cell/taken in by phagocytes.

*Phagocyte puts antigen protein on C-S-M.

*Receptors on T (helper) cell complementry and bind to protein.

*Ativates T cell to divide (by mitosis).

*The cloned cells;

Develop memory cells, simulate phagocytes to engulf pathogens, simulate B-cells to divide+secrete their antibody. ALSO activates T C cells.

Cytotoxic cells kill abnormal cells.

It produces a protein called perforin.

This makes holes in the membrane of the C-S-M.

This makes the cell freely-permeable. The cell dies x-x.

How do Lymphocytes recognise cells belonging to the body? (cell mediated immunity)

*In the fetus lymphocytes collide constantly with the body's own material.

*Infection is rare because of protection from the mother and placenta.

*Some Lyphocyte receptors fit with own cells. The die or are suppressed. 

*Only remaining complementry to non-self material. 

*In adults lymphocytes are produced in bone marrow. They only encounter self-antigens. Any lymphocytes that have a immune response to self-antigens are programmed to die.

*No clones of these will appear in the blood.

Humoral…