Immune Response

• Inflammatory mediators include histamine, prostaglandins, leukotrienes, cytokines, chemokines, and interleukins.
• Complement proteins play a role in opsonization, lysis of bacteria, and recruitment of other immune system components.
• Antibody production is initiated when an antigen enters the body and stimulates B cell activation.
• Antibody molecules have two identical heavy chains and two light chains held together by disulfide bonds.
• Antigens are molecules that stimulate an immune response, while antibodies bind to antigens on pathogens or abnormal cells.
• Phagocytosis involves engulfing foreign particles by macrophages through receptor-mediated endocytosis.
• The innate immune system is the first line of defense against infection and consists of physical barriers such as skin and mucous membranes, phagocytes (macrophages), natural killer cells, complement proteins, cytokines, interferons, and inflammation.
• Complement proteins are enzymes involved in opsonization, lysis of bacteria, and activation of other components of the immune system.
• The humoral response involves the secretion of antibodies from plasma cells into the bloodstream.
• Inflammatory mediators include histamine, prostaglandins, leukotrienes, bradykinin, and platelet activating factor, which cause vasodilation, increased vascular permeability, pain, fever, and recruitment of white blood cells.
• Cytokines are signaling molecules produced by various cell types that regulate immune responses and have diverse effects on target cells.
• Interferons are glycoprotein hormones secreted by virus-infected cells that inhibit viral replication and activate immune defenses.
• T lymphocytes recognize specific antigenic determinants presented by MHC class II molecules on APCs.
• Tumor necrosis factors (TNF) are cytokines that induce apoptosis in tumors and infected cells.
• Interleukins are cytokines secreted by T helper cells that promote B cell differentiation into plasma cells and activate cytotoxic T cells.
• Chemical signals released during inflammation attract neutrophils, monocytes/macrophages, eosinophils, basophils, and T cells to the site of infection.
• Interferons are cytokines produced by virus-infected cells that inhibit viral replication and enhance MHC expression.
• B lymphocytes recognize specific antigens directly or through antibody bound to an antigen.
• Macrophages are long-lived phagocytes that can differentiate into epithelioid cells, giant cells, or multinucleated cells.
• Tumor necrosis factors (TNF) are cytokines released by activated macrophages and T cells that induce apoptosis in tumor cells and infected cells.
• Interleukins are cytokines that promote growth and differentiation of T cells and B cells.
• Colony stimulating factors (CSF) are cytokines that stimulate production of granulocytes, monocytes, eosinophils, basophils, and red blood cells.
• IL-1 is an inflammatory cytokine that stimulates B cell proliferation and antibody production.
• IL-4 is a Th2 differentiation factor that enhances humoral immunity.
• Transforming growth factor beta (TGFβ) is a cytokine that suppresses inflammation and promotes tissue repair.
• Histamine is involved in vasodilation, increased vascular permeability, and smooth muscle contraction.
• Chemotactic factors attract leukocytes to sites of infection or inflammation.
• Phagocytic cells engulf bacteria marked with antibodies and complement components.
• IL-2 is produced by helper T cells and promotes the clonal expansion of cytotoxic T cells and B cells.
• Activation of the complement system leads to formation of C3b, which binds to microbes and activates other components of the complement cascade.
• Antibodies bind to pathogens and mark them for destruction by other immune system components.
• Antibodies bind to pathogens and activate complement proteins.
• Innate Immunity

  • Recognition of pathogens by pattern recognition receptors (PRRs).
  • Activation of innate immune cells (e.g., macrophages, neutrophils) and their roles in phagocytosis, inflammation, and cytokine production.
  • Complement system activation and its functions in opsonization, inflammation, and membrane attack complex formation.
• Humoral immunity involves the production of antibodies that can neutralize or eliminate pathogens directly or indirectly through complement activation.
• Antigen presentation involves MHC class I and II molecules, antigen processing, and presentation pathways
• According to the clonal selection theory, antigen-specific lymphocytes expand and differentiate upon encountering antigens
• Immunological memory involves the generation of memory T cells and memory B cells for long-term protection against pathogens
• Pattern recognition receptors 


  recognize specific molecular patterns commonly found on pathogens and are expressed on cells of the innate immune system.
• The adaptive immune response is characterized by its ability to generate immunologic memory, which allows for rapid responses to subsequent exposures to the same pathogen.
• Adaptive immunity can be further divided into humoral immunity mediated by soluble proteins called antibodies or B cells, and cellular immunity mediated by T cells.