then the innate immune response begins. The cells of the immune system determine “self” from “non- self” by recognizing molecules on the microbe surface. Macrophages and dendritic cells are immune cells (phagocytes) that reside within the tissue. Neutrophils are phagocytes that reside in the blood but can extravagate into tissue during inflammation. There are circulating proteins, called complement, that either kill microbes or mark them for effective phagocytization.
Complement is a system of plasma proteins that interacts with pathogens to mark them for destruction. 1. Alternative pathway : pathogen surfaces 2. Mannan binding-lectin pathway : lectin binding to pathogen surfaces 3. Classical pathway : Ag:Ab complexes Functions: phagocytosis inflammation lysis
Through pattern recognition ( genetically programmed ) PAMPS Toll like receptors
Activates vascular endothelium Activates lymphocytes Local tissue destruction Increases access of effector cells Fever, production of IL-6
Activates vascular endothelium Increases vascular permeability Increased entry of IgG, complement, and cells to tissues Increased fluid drainage to lymph nodes Fever Mobilization of metabolites Shock
Lymphocyte activation Increased antibody production Fever Induces acute-phase protein production
Activates NK cells Induces the differentiation of CD4 T cells into T H 1 cells
Hypothalamus increased body temperature Fat, muscle protein & energy mobilization to allow increased body temperature decreased viral & bacterial replication & increased antigen processing & specific immune response
Antigen specific response to antigen / pathogen Key feature if this system is that subsequent exposure to the initial antigen leads to more rapid and vigorous response ( Immunological memory) T and B lymphocytes drive this response from common stem cell
T-cell : cellular immunity through differentiation in TH-1 ( cellular )and TH-2 pathways ( humoral) B-cell clonal response initially producing IgM and then IgG to infections : Memory cells produced that react much faster to future threats from the same pathogen.
Positive and negative selection of t-cells CD-4, CD-8 and T-killer cells emerge Thymus continues to work in adult life especially when t-cell pool is damages as in AIDS and cancer chemotherapy