CD8+ cells

Class I. These molecules are expressed on the surfaces of all nucleated cells and are recognized by CD8+ cells, also known as cytotoxic T cells. There are three subclasses of MHC class I molecules called HLA-A, HLA-B, and HLA-C. 

Humphreys TL, Baldridge LA, Billings SD, Campbell JJ, Spinola SM. Trafficking pathways and characterization of CD4 and CD8 cells recruited to the skin of humans experimentally infected with Haemophilus ducreyi. Infect Immun 2005 73 3896-902. 

Immature CD4 CD8 cells and CD4+CD8+ cells respond very well to CXCL12, whereas CD4+CD8 or CD4"CD8+ cells respond poorly. Early... 

Iyengar S, Schwartz DH, Hildreth JE. T cell-tropic HIV gpl20 mediates CD4 and CD8 cell chemotaxis through CXCR4 independent of CD4 implications for HIV pathogenesis. J Immunol 1999 162(10) 6263—6267. 

Ahmed RK, Nilsson C, Biberfeld G, Thorstensson R. Role of CD8+ cell-produced anti-viral factors in protective immunity in HIV-2-exposed but seronegative macaques resistant to intrarectal SIVsm challenge. Scand J Immunol 2001 53 245-253. 

Chipeta, J., et al. CD4+ and CD8+ cell cytokine profiles in neonates, older children, and adults increasing T helper type 1 and T cytotoxic type 1 cell populations with age, Cell. Immunol., 183, 149, 1998. 

CD8 Cell associated Antigen presented by MHC I clonal expansion of CD8 cells Activation of cytotoxic (CD-8) T cells Contact dermatitis (poison ivy) Chronic hypersensitivity pneumonitis... 

CD8 + T cells are driven by MHC class I molecules and do not require professional APC. CD 45 Ro + CD8 + T cells are increased in early infection and are often maintained in symptomatic disease however, dendritic cells are important in stimulating cytotoxic T lymphocyte (CTL) responses in unprimed CD8 + T cell. CD8 cells may also be subdivided based on their cytokine secretion. CD8 CTL clones produce INF-y, IL-6, TNF-a, and ILIO, whereas suppressor cells produce high levels of cytokines associated with Th-2 cells, including IL-4 and low levels of IL-5, IL-6, and IL-10. 

Fig. 1. Organ/cellular pathways in the induction of CD8+ suppressor cells by the injection of antigen into the anterior chamber (AC). he injection of antigen into the AC induces a recruitment of F4/80+ monocytic cells to the iris. Interactions with iris monocytic cells, antigen and GF-p in aqueous humor induces an immunosuppressive phenotype in the recruited cells. hese cells then recirculate from the AC to the thymus and the spleen. In the spleen, F4/80+ cells interact with B cells, peripheral NK cells, recent thymic NK emigrants and CD8+ cells with the generation of CD8+ suppressor cells that effect the suppression of a D FI reaction.

Figure 1 Continued on next page) Immunopotentiating reconstituted influenza virosomes (IRIV) induced antigen specific proliferation of CD4+CD45RO+ cells. (A) Peripheral blood mononuclear cells (PBMQ from healthy donors n=3) were cultured in the absence of stimuli (Neg), in the presence of IRIV (V), and in the presence of control liposomes (L) at the indicated dilutions. Proliferation was measured on day 6 of culture by H-thymidine incorporation. (B) Cord blood mononuclear cells from two donors were cultured in the absence of stimuli (Neg) or in the presence of phytohaemag-glutinin (PHA), concanavalin A (ConA), IRIV (V) or L at the indicated concentrations. Proliferation was measured on day 3 of culture for PHA and ConA cultures and on day 6 for IRIV and L stimulated cultures. (Q Purified CD4+ or CD8+ cells were cocultured with autologous irradiated PBMC in the absence of stimuli (Neg) and in the presence of IRIV (V) at the indicated concentrations. Proliferation was measured on day 6 of culture by H-thymidine incorporation. (D) Purified CD4/CD45RA+ cells and CD4/CD45RO-I-cells were isolated from PBMC of one healthy donor and cocultured with autologous irradiated PBMC in the presence of IRIV (V) or L at the indicated concentration. Proliferation was measured on day 6 of culture by H-thymidine incorporation. Source From Ref 6.

The TCR is composed of integral membrane protein that recognizes the antigen and as a consequence its activation produces an immune response to eliminate the antigen. This process results in the development of CD4+ or CD8+ cells from the precursor T cells. It involves other cell surface receptors and downstream signal transduction mechanisms. 

IFN-y modulates a number of components of the immune response. This is the only type II IFN whereas there are more than 20 types of type I IFNs (IFN-a, IFN-(3, IFN-w and IFN-t). It is not related to type I IFNs, has separate receptors and is encoded by a different chromosomal locus. IFN-y is produced by activated T lymphocytes (THi and CD8+ cells), NK cells, B cells, NKT cells and professional APCs. It promotes the activity of cytolytic T lymphocytes, macrophages and NK cells. The cell self-activation and activation of nearby cells in part may result from IFN-y production by professional APCs, which include monocyte/macrophage and dendritic cells. The early host defense against infection is likely to utilize IFN-y secreted by NK and professional APCs. In acquired immune responses, T lymphocytes are the major source of IFN-y. 

Type IV Reactions Also termed delay-type hypersensitivity reaction, these take 48-72 h to develop and are not antibody-mediated. Antigens are recognized by CD4+ and/or CD8+ cells in the context of MHC class restrictions on APCs. These reactions are T-cell-mediated where activated T cells release cytokines, resulting in the development of granulomas from macrophages. These mechanisms are responsible for symptoms that may include transplant rejection, contact dermatitis, leprosy, tuberculosis and sarcoidosis. 

During infancy, wheezing is also associated with the sequestering of CD8+ cells in the airways during an acute asthma attack, and asthma deaths are associated with activated CD8+ T-cell infiltration into peribronchial tissue. 

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