Immune System Overview

GOT DEFENSE?

ANATOMY OF THE IMMUNE SYSTEM The immune system is localized in several parts of the body –immune cells develop in the primary organs - bone marrow and thymus –immune responses occur in the secondary organs

IMMUNITY Innate Players Macrophages Granulocytes Natural killer cells Complement Other chemicals Characteristics Action is immediate; minutes to hours Response is nonspecific First line of defense against invading pathogens Response is not enhanced on repeated exposure to pathogen Adaptive Humoral Cell-Mediated Players Antigen Presenting Cells T cells B cells Antibodies Characteristics Action requires days to develop Response is specific Prevents progression to disease Response is enhanced on repeated exposure to pathogen

Immune System: Innate and Adaptive

Cytokines Soluble protein molecules used by cells of the immune system to communicate.Soluble protein molecules used by cells of the immune system to communicate. Functions include:Functions include: –Mediation of natural immunity –Regulation of lymphocyte activation, growth, and differentiation –Regulation of immune-mediated inflammation –Stimulation of immature leukocyte growth and differentiation Interleukins (IL-2 & IL-4), interferons (  ), tumor necrosis factors (  and  ), and transforming growth factor Interleukins (IL-2 & IL-4), interferons (  ), tumor necrosis factors (  and  ), and transforming growth factor 

Immune System: Innate and Adaptive

2. The immune system consists of: Anatomic barriers (Skin,mucous membranes) Physiological barriers (temperature, pH) Phagocytic Barriers (cells that eat invaders) Inflammatory barriers (redness, swelling, heat and pain) Innate (non-specific) immunity Adaptive (specific) immunity

NeutrophilEosinophil Basophil

MonocytesDendritic cell

Immune System: Innate (phagocytosis) 1. Phagocytic cells: Macrophage, Neutrophil, and Dendritic cells. 2. Phagocytosis serves two key functions: Killing microbes Antigen (Ag) Presentation

GOT DEFENSE?

Immune System: Innate (phagocytosis)

Opsonization

Inflammation A hallmark of innate immunity Local accumulation of immune cells and molecules against microbes Function to eliminate infections but often cause tissue damage & diseases Immune System: Innate

Inflammatory Response

Inflammation

Inflammatory Response

The immune system consists of: Anatomic barriers (Skin,mucous membranes) Physological barriers (temperature, pH) Phagocytic Barriers (cells that eat invaders) Inflammatory barriers (redness, swelling, heat and pain) Antigen specificity Diversity Immunological memory Self/nonself recognition Innate (non-specific) immunity Adaptive (specific) immunity

Adaptive Immunity

Major Histocompatibility Complex (MHC) Also known as Human Leukocyte Antigen (HLA) Membrane bound, not soluble “Present” processed protein antigens (peptides) to naïve T cells MHC I -> produced by almost all nucleated cells, present antigen to CD8+ cytotoxic T lymphocytes (CTL) MHC II -> produced by “professional” antigen presenting cells, present antigen to CD4+ lymphocytes (T helper cells)

Produced by T lymphocytes Are surface bound, not secreted Recognize “processed” peptide antigens presented on MHC molecules Heterodimer of  or  chains Like antibodies, each chain has a variable and constant region Also undergo gene rearrangement prior to expression T Cell Receptors (TCRs)

The immune system has evolved to: Protect against invading pathogens or foreign substances. Maintain tissue homeostasis. Meanwhile, microbes have evolved to survive in the host.