Cell-mediated immunity

Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

Historically, the immune system was separated into two branches: humoral immunity, for which the protective function of immunization could be found in the humor (cell-free bodily fluid or serum) and cellular immunity, for which the protective function of immunization was associated with cells. CD4 cells or helper T cells provide protection against different pathogens. Naive T cells, mature T cells that have yet to encounter an antigen, are converted into activated effector T cells after encountering antigen-presenting cells (APCs). These APCs, such as macrophages, dendritic cells, and B cells in some circumstances, load antigenic peptides onto the MHC complex of the cell, in turn presenting the peptide to receptors on T cells. The most important of these APCs are highly specialized dendritic cells; conceivably operating solely to ingest and present antigens. ^[1]

Activated Effector T cells can be placed into three functioning classes, detecting peptide antigens originating from various types of pathogen: The first class being Cytotoxic T cells, which kill infected target cells by apoptosis without using cytokines, the second class being TH1 cells, which primarily function to activate macrophages, and the third class being TH2 cells, which primarily function to stimulate B cells into producing antibodies.^[2]

The innate immune system and the adaptive immune system each comprise both humoral and cell-mediated components.

Cellular immunity protects the body by:

T-cell mediated immunity or T-cell immunity : activating antigen-specific cytotoxic T cells that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;
activating macrophages and natural killer cells, enabling them to destroy pathogens; and
stimulating cells to secrete a variety of cytokines that influence the function of other cells involved in adaptive immune responses and innate immune responses.

Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells. It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria. It also plays a major role in transplant rejection.

References

↑ Janeway, Charles; Travers, Paul; Walport, Mark; Shlomchik, Mark (2001). Immunobiology (5th ed.). New York: Garland Science. ISBN 0-8153-3642-X. Retrieved 24 January 2017.
↑ Janeway, Charles; Travers, Paul; Walport, Mark; Shlomchik, Mark (2001). Immunobiology (5th ed.). New York: Garland Science. ISBN 0-8153-3642-X. Retrieved 24 January 2017.

Cell-mediated immunity (Encyclopædia Britannica)
Chapter 8:T Cell-Mediated Immunity Immunobiology: The Immune System in Health and Disease. 5th edition.

Antigens	Antigen Superantigen Allergen Hapten Epitope Linear Conformational Mimotope Antigen presentation/Professional APCs: Dendritic cell Macrophage B cell Immunogen
Antibodies	Antibody Monoclonal antibodies Polyclonal antibodies Autoantibody Microantibody Polyclonal B cell response Allotype Isotype Idiotype Immune complex Paratope
Immunity vs. tolerance	action: Immunity Autoimmunity Alloimmunity Allergy Hypersensitivity Inflammation Cross-reactivity inaction: Tolerance Central Peripheral Clonal anergy Clonal deletion Tolerance in pregnancy Immunodeficiency
Immunogenetics	Affinity maturation (Somatic hypermutation Clonal selection) V(D)J recombination Junctional diversity Immunoglobulin class switching MHC/HLA

Lymphocytes

Substances

Hypersensitivity and autoimmune diseases (279.5–6)

Type I/allergy/atopy
(IgE)

Foreign	Atopic eczema Allergic urticaria Allergic rhinitis (Hay fever) Allergic asthma Anaphylaxis Food allergy common allergies include: Milk Egg Peanut Tree nut Seafood Soy Wheat Penicillin allergy
Autoimmune	Eosinophilic esophagitis

Type II/ADCC

- IgM
- IgG

Foreign

Hemolytic disease of the newborn

Autoimmune

Cytotoxic	Autoimmune hemolytic anemia Immune thrombocytopenic purpura Bullous pemphigoid Pemphigus vulgaris Rheumatic fever Goodpasture's syndrome Guillain–Barré syndrome
"Type V"/receptor	Graves' disease Myasthenia gravis Pernicious anemia

Type III
(Immune complex)

Foreign	Henoch–Schönlein purpura Hypersensitivity vasculitis Reactive arthritis Farmer's lung Post-streptococcal glomerulonephritis Serum sickness Arthus reaction
Autoimmune	Systemic lupus erythematosus Subacute bacterial endocarditis Rheumatoid arthritis

Type IV/cell-mediated
(T cells)

Foreign	Allergic contact dermatitis Mantoux test
Autoimmune	Diabetes mellitus type 1 Hashimoto's thyroiditis Multiple sclerosis Coeliac disease Giant-cell arteritis Postorgasmic illness syndrome Reactive arthritis
GVHD	Transfusion-associated graft versus host disease

Unknown/
multiple

Foreign	Hypersensitivity pneumonitis Allergic bronchopulmonary aspergillosis Transplant rejection Latex allergy (I+IV)
Autoimmune	Sjögren's syndrome Autoimmune hepatitis Autoimmune polyendocrine syndrome APS1 APS2 Autoimmune adrenalitis Systemic autoimmune disease

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Cell-mediated immunity

References

Further reading