kidney

IMMUNITY Dr Farzana Salman

Immunity The ability of the body to resist all types of organisms or toxins that tend to damage the tissues and organs is called immunity. Innate immunity Acquired immunity

INNATE IMUNITY Prior to exposure to pathogen. Non specific Does not improve after exposure to antigen No memory

Innate Immunity Phagocytosis of bacteria and other invaders by WBC and cells of tissue macrophage system. Destruction of swallowed organisms by acid secretions of stomach and digestive enzymes. Resistance of skin to invasion by organisms . Chemical compounds present in blood Lysozyme Basic polypeptides Complement complex.

Acquired Immunity Specific immunity Develops after exposure to antigen Improves on repeated exposure Memory cells are formed

Acquired Immunity Humoral / B- cell immunity B lymphocytes Antibodies Cell mediated immunity / T cell immunity T lymphocytes Activated T lymphocyte

Antigens Molecules that react with antibodies . Nonself Molecular weight = 8000 or greater Epitopes – regularly recurring molecular groups on the surface of large molecules.

Preprocessing of T/B Lymphocytes Pluripotent hematopoietic stem cell Lymphoid progenitor cells Thymus ---- T lymphocytes Liver and bone marrow---- B lymphocytes

Clones of Lymphoytes All different lymphocytes that are capable of forming one specific antibody or T cell are called clones of lymphocytes.

Mechanism for activating a clone of lymphocytes. Role of macrophages in the activation process. Antibodies formation Memory cells

ANTIBODIES Immunoglobulins Molecular weight = 160,000- 970,000 20% of plasma proteins Heavy and light chains

Affinity Constant Ka = Concentration of bound antibody –antigen / Concentration of antibody x Concentration of antigen.

Classes of Antibodies IgM IgG IgA IgD IgE

IgG – bivalent 75% antibodies in a normal person Predominant in secondary response Cross the placenta Activate compliment system Proinflammatory and antiinflamatory

IgE --- Involved in Allergy Serum IgE levels are increased in parasitic infestations IgM—10 binding sites Main antibody formed during primary response. Activate compliment system

IgA--- Main antibody in secretions such as colostrum,saliva,tears,respiratory ,intestinal and genital secretions. IgD– No known antibody function Act as antigen receptor . Present on surface of many B lymphocytes.

Mechanism of Action of Antibodies Direct attack on invader Activation of Complement system.

Direct Action of Antibodies Agglutination Precipitation Neutralization Lysis

Agglutination

Complement system For Antibody Action 20 proteins (enzyme precursors) Principal actors in this system are 11 proteins C1 to C9 B and D

Classic pathway Alternative pathway

Classical Pathway of compliment system

C3b---Opsonization and phagocytosis C5b6789--- Lytic complex Agglutination Neutralization of viruses C5a---- Chemotaxis C3a,C4a,C5a---- Activation of mast cells and basophils Inflammatory effects

Alternate Pathway Polysaccharides of invading organisms combine with Factor B and D. This complex activates C3 to C3a and C3b Onwards reactions are same as in classic pathway