Lec.10 Immune response كلية المأمون الجامعة\قسم تقنيات التحليلات المرضية مادةالمناعة-النظري/المرحلةالثالثة م.م.رشد اياد عبدالحميد

Infection of the human body by pathogenic microorganisms triggers the immune response. It occurs in a two-step process: innate immune response which occur within minutes and last for several days, its purpose is to recognize and clear most of microbes or damaged tissues; and the adaptive immune response follow and peaks within the following weeks resulting in immunological memory that can last for the life of the individuals. The adaptive immune response involve humeral and cellular immunity

Humeral immunity (Antibody mediated immunity): -It is a protection provided by antibodies present in body fluid (humor) - When B-cells recognize the antigen it proliferate and mature into clones of plasma cell and memory B –cell which secrete antibody into the circulation which bind to the antigen and eliminate it

Clonal Selection of B Cells is caused by Antigenic Stimulation

Cellular immunity (Cell mediated immunity): When T-cells recognize the antigen it differentiated into: T-helper cell which indirectly act against the infected cell by releasing the cytokines that enhance inflammatory response or activating other lymphocyte or macrophages. - Cytotoxic T- cell which directly kill the infected cell especially (virus infected cells and tumor cells). -Memory T-cells which remember a specific antigen.

Primary and secondary immune response

  Primary immune response Secondary immune response 1. lag phase is longer than (4-7 days) 1. lag phase is shorter than(1-4 days) 2. Ab of IgM class 2.Ab of IgG class 3.Low affinity Ab 3. High affinity Ab 4.Ab titer is low 4.Ab titer is high 5.The host exposure for the first time so no memory cell 5.Host exposure for the second time there is memory cell 6.Ab titer decline rapidly 7.Naive -lymphocyte 6.Ab titer decline slowly 7. Memory -lymphocyte

Regulation of immune response: Immune responses are regulated interaction of cells and mediators by mechanisms to prevent anti- self reactivity. Failure of regulatory control can occur resulting in: - Enhancement of immune response and generate autoimmune disease. -Decrease of immune response may lead to an immunodeficiency state. - Shift in immune response can lead to allergy.

The role of T- helper cells in regulation of immune response: Th cells regulate the immune system by cytokines (Interleukins). Cytokines from Th1 regulate cellular immunity by regulate the proliferation and activity of other cells of the immune system such as ( T-cytotoxic cell(TC- cell), NK cells, macrophages, neutrophils ) and other cell. Cytokines from Th2 regulate humoral immunity by regulate the proliferation and activity of B-cell.

The role of T- regulatory cell(T-reg) in regulation of immune response: 1- Regulation of Th1 and Th2 cytokine production. 2- Production of suppressive cytokines such as: IL-10 which inhibit the function of antigen presenting cell such as macrophage. -TGF-ß inhibit T-cell proliferation.