1. Immune response
Pathophysiology

2. Immune response Body’s response to antigens
It is the third line of defense
Antigens include – viruses, bacteria, fungi, parasites, pollens, food, venom, drugs, vaccines, transfusion. Transplanted tissues
IR is Mediated by immunoglobulins and lymphocytes
B lymphocytes – multiply and produce Ig [clonal selection
T lymphocytes – directly attack Ag in cell-mediated immunity [CMI]
Responsible for acquired [after birth] immunity

3. Lymphoid organs – sites of B ,T cell differentiation

5. Induction of IR
Antigens – have a part [antigenic dterminant/ epitope] which can be bound by a paratope/Ag binding site. Immunogenicity depends on size, foreignness, complexity & amount. The body is tolerant to self Ag. Haptens are too small on their own but become immunogenic when combined with larger molecules
Blood group antigens – Antigen A, antigen B, Antigen A and B. blood group O has neither of the antigens
Rhesus positive [DD or Dd genotype]. Rh negative [dd] do not express the Ag

6. Humoral immunity
After generation of clonal diversity become B lymphocytes
B cells are activated by Ag to multiply [clonal selection] into:
Plasma cells which secrete Ig
Memory cells responsible for subsequent response to Ag

7. Immunoglobulins
Five types – IgA, IgD, IgE, IgG, IgM [alpha, delta, Epsilon, gamma, Mu]– with antigenic, structural and functional differences

9. Functions of Ig
Neutralizing bacterial toxins – form Ag-Ig complexes which precipitate out of body fluids/solutions and get phagocytosed
Neutralizing viruses – and prevent viral entry into cells. Essence of vaccination
Opsonizing bacteria – opsonise and induce opsonization by complement system
Activation of inflammation – while the Fab binds to Ag, Fc amplify the inflammatory response

10. Secretory immune system
Ig produced in body fluids other than blood: tears, sweat, saliva, mucus, breast milk to protect external body surfaces.
Produced by B cells in the organs

11. Primary and secondary response

13. Cell mediated immunity
Mediated by T cells which mature in the thymus
Lymphokine producing cells - transfer delayed hypersensitivity, activate other cells [macrophages]
Cytotoxic cells (Tc) – attach Ag, destroy cells with foreign Ag
T helper cells – Th – control CMI and humoral immunity
Suppressor T cells – Ts – control CHI and HI
Natural killer cells – kill Ag infected and tumor cells

14. Effects of CMI
Cytotoxicity – direct cellular killing of virally infected cells, tumors or foreign grafts. APC express Ag on their MHC [Histocompatibility antigen complex]
Delayed hypersensitivity – influence of other cells
Memory – responsible for a faster response against subsequent antigenic challenges
Control – of HI and CMI