Effector lymphocytes

This class of lymphocytes differentiates from immuno-logically incompetent hematopoietic stem cells of the bone marrow within the thymus - hence, the name thymus-dependent (T-) lymphocytes. Two major subclasses develop simultaneously, T-helper lymphocytes (Th) and cytotoxic effector lymphocytes (Tc). The cytotoxic T-lymphocytes (carrying on the surface the differentiation marker CD8) destroy cells, which cany their cognate antigen bound to MHC class I molecules on the surface by inducing apoptosis. From an evolutionary point of view Tc cells appear to have developed predominantly to cope with vims infections. As vituses can only replicate within cells, Tc eliminate them by destroying their producers. 

The lymph node harbors a composite population of dendritic cells (DCs)—residents and emigrants—capable of selection, stimulation and elimination of effector lymphocytes. These cells trigger adaptive immunity and/or tolerance. In the human lymph node T-cell compartment, two primary subsets of DCs, compared to six in mice, have been identified monocytoid CD 1 lb CD 1 and plasmacytoid interferon (IFN)-a produc-... 

D. H. Irvine and M. A. Savagean, Network regulation of the immune response alternative control points for suppressor modulation of effector lymphocytes. J Immunol 134(4) 2100-2116 (1985). 

From what is known about CMV-encoded chemokines and chemokine receptors, it appears that their participation in immune evasion would be mainly at the level of viral dissemination sheltered from the immune system through (cell-to-cell) passage and movement of receptor bearing infected cells bidirectionally across endothelial barriers. In addition, the ability of pUS28 to withdraw CC chemokines from the environment of infected cells could also confer a measure of immune evasion by blunting effector lymphocyte migration and activation. 

Autochthonous lymphocytes activated vitro with phytohemaglutinin (PHA) and applied to subcutaneous metastatic nodules resulted in a greater percent regression than non-activated lymphocytes but the degree of regression in those nodules which were affected was not significantly different from the control group.This study reemphasized the need for effector lymphocytes at the site of the tumor. 

Plant M, Lichtenstein LM, Henney CS. Increase in histamine receptors on thymus-derived effector lymphocytes during the primary immune response to aUoantigens. 

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