Release of endotoxins leading to inflammatory cytokines.
Cardinal Signs of Inflammation
Heat
Redness
Swelling
Pain
Mechanism:
Inflammatory cytokines cause vasodilation, increasing blood flow.
Endothelial cell contraction increases permeability, leading to fluid leakage.
Fluid compresses pain receptors, inducing pain.
Cell Adhesion Molecules
Enhance margination response:
P-selectins, E-selectins, ICAMs, VCAMs.
Promote rolling and migration of leukocytes to injury site via positive chemotaxis.
Effects of Inflammatory Cytokines
Cytokines such as IL-1, TNF-alpha, and IL-6:
Cause fever by acting on the hypothalamus.
Stimulate liver to produce C-reactive protein (CRP).
Trigger increased leukocyte production in bone marrow via leukocytosis.
Phagocytosis
Phagocytes:
Consume bacteria via pseudopods, forming a phagosome.
Phagosome fuses with lysosome for breakdown.
Neutrophils:
May use oxidative burst for bacteria.
Release chromatin to tag bacteria for destruction.
Complement System
Activation Pathways:
Classical (antibody-mediated), Alternative (direct binding), Lectin pathways.
Effects:
Produces membrane attack complex (MAC) for lysis of bacteria.
Enhances opsonization and inflammatory response.
Response to Viral Infections
Infected Cells:
Produce interferons (alpha, beta, gamma).
Functions of Interferons:
Alpha & Beta: Stimulate nearby healthy cells to produce antiviral peptides.
Gamma: Activates macrophages and enhances their response.
Toll-like Receptors (TLRs)
Types:
11 types, with 10 known functions.
Result:
Signal proteins for chemotaxis, production of TNF-alpha, IL-1 beta, etc.
Adaptive Immune System
Interaction of Macrophages with Lymphocytes:
Antigen presentation via MHC II molecules.
B Lymphocyte Activation:
B cells recognize antigens; require T cell help for full activation.
Activated B cells undergo clonal expansion and differentiation.
Interleukins:
IL-4 (stimulates B cell proliferation) and IL-5 (stimulates differentiation into plasma cells).
Humoral Immunity
Function:
B cells produce antibodies against exogenous antigens.
Memory B cells and plasma cells persist for future responses.
Cell-Mediated Immunity
Cytotoxic T Cells:
Target and destroy virus-infected or cancerous cells.
Use perforins and granzymes to kill infected cells.
Natural Killer Cells:
Part of innate immunity but similar mechanisms to cytotoxic T cells.
Recognize the absence of MHC I or abnormal MHC.
Summary
The lecture covered the key components of the innate and adaptive immune systems, emphasizing their roles in inflammation, pathogen recognition, and response mechanisms.