ENH220 Lec 2 Immunity, Hypersensitivity, Allergy etc.

Innate immunity

Body's first line of defense providing immediate and nonspecific protection against pathogens; includes physical barriers, cellular defenses and chemical defenses

Innate immunity physical defenses

skin acts as barrier preventing entry of pathogens; mucous membranes line entry points into body and cells secrete mucus that traps and expells pathogens

innate immunity cellular defenses

phagocytic cells ex. neutrophils and macrophages are white blood cells that patrol tissues and engulf invading pathogens; natural killer cells are specialized immune cells that identify and destroy infected or abnormal host cells, ex. those infected by viruses or cancer cells

innate immunity chemical defenses

complement system including circulating proteins (complement proteins) that help in opsonization of pathogens (marks pathogens for destruction); antimicrobial peptides are released by cells at sites of infection and disrupt microbial structures including cell membranes, effectively killing pathogens

Complement pathways

antibodies recognize antigens; first complement pathways attracts immune cells to the site of an infection or injury and promotes inflammation; alternate pathway coats the surface of the cell and attack complex goes into the cell through osmolysis to burst/kill the cell

Innate immunity functions

rapid response; non-specific defense; inflammation; fever; activation of adaptive immunity; lack specificity and memory; some pathogens have evolved mechanisms so may not be sufficient to eliminate certain pathogens

Adaptive immunity

provides specific long-lasting protections against pathogens; actions of T and B cells (lymphocytes); memory cells lead to immunological memory

Humoral immunity

also called antibody-mediated immunity; primarily revolves around production and action of antibodies; B cell lymphocytes; antibodies neutralize bacteria by various means ex. preventing them from attaching to host cells or marking them for destruction by other immune cells; many mechanisms that serve as main defense against bacteria/toxins

Cell-mediated immunity

centered around actions of T cell; combats broader range of threats ex. viruses, fungi, parasites; crucial when dealing with intracellular pathogens because it enables immune system to recognize and eliminate infected cells, preventing the pathogen from spreading; causes organ rejection in some cases as transplanted organ seen as foreign object

IgG

This is a smaller antibody and is the principal antibody type produced in response to the majority of infectious agents

IgM

A larger antibody and is particularly efficient at binding to and neutralizing fungi

IgE

Concentrations are increased in individuals with allergies

IgA

Helps prevent the absorption of harmful ingested or inhaled antigens by forming antigen-antibody complexes

IgD

Present in small quantities in the blood

Hypersensitivity reactions

exaggerated or abnormal immune responses to antigens

Type I hypersensitivity

IgE mediated; quick onset after exposure; allergic reactions ex. bee stings, latex, certain medications ex. penicillin

Type II hypersensitivity

Cytotoxic/antibody-mediated; hemolyti reactions, goodpasture syndrom, hyperacute graft rejection

Type III hypersensitivity

Immune complex/IgG/IgM mediated; immune complex deposition; hypersensitivity pneumonitis, systemic lupus erythematosus, polyarteritis nodosa, serum sickness

Type IV hypersensitivity

Delayed or cell-mediated; delayed reactions; chronic graft rejections; PPD test; latex; nickel; poison ivy

Immune response genes

relate to HLA complex on chromosome 6; they regulate immune responses via T and B cell function; impact infection resistance, tumor defense, autoimmune susceptibility

Autoimmune disease

self-antigen alteration; cross-reactive antibodies; regulatory T cell dysfunction contributes to autoimmune reactions

Growth of neoplasms

derivation from a single abnormal cell (stem cell); cell has undergone genetic changes gives rise to population of cells with similar characteristics

tumor heterogeneity

neoplasms exhibit a high degree of heterogeneity; genetic mutations and microenvironmental factors; mixture of cell types within the same tumor

Progression of genetic changes leading to cancer

activation of oncogenes; loss of function of tumor suppressor genes; additional random genetic changes

HPV and cervical cancer

HPV effects epithelial cels in cervical mucosa; HPV DNA integrates into the cellular genome when causing cancer; can integrate into tumor cell DNA and develop cancer

Apoptosis

programmed cell death; irremediable changes to DNA resulting in cell death within the mutated cell; fundamental process that helps regulate survival and lifespan of cells; crucial role in maintaining balance between cell growth and cell death

Oncogenes

driving factor of cancer development; stimulates cell proliferation when reacted; mutation leads to inappropriate cell proliferation