Memory cells, effector phenotypes

Early Memory Cells That Display an Effector Phenotype... 

In order to address this problem, it has been su ested that, at least in mice, ThI and Th2 cells may represent memory cells that have matured into different functional phenotypes in the face of repeated stimulation by specific antigen. This hypothesis invokes the putative existence of antigen-naive precursor T lymphocytes (Tup) which secrete principally IL-2 and develop into early memory ThO effector cells after first encounter with specific antigen (Swain etal., 1990). These cells then terminally differentiate into ThI or Th2 cells following repetitive antigen stimulation. 

The effects of Pb on the mixed lymphocyte response (MLR) have been examined in prior studies. McCabe and colleagues [53] and Farrer and colleagues [54] demonstrated that Pb in vitro at very low concentrations (0.1 pM = 2 pg/dL) significantly enhanced the proliferation and expansion of murine alloreactive CD4+ T lymphocytes in the MLR. The expanded T cell population was found to have a high density of CD4 molecules on the cell surface making them phenotypically similar to memory/effector T lymphocytes. In a study using Lewis strain rats, Razani-Boroujerdi and coworkers [55] also found evidence for Pb-induced stimulation of the in vitro MLR. 

Huehn J. Siegmund K. Lehmann JC. Siewert C. Haubold U. Feuerer M. Debes GF. Lauber J. Frey 0. Przybylski GK. Niesner U. de la Rosa M. Schmidt CA. Brauer R. Buer J. Scheffold A. Hamann A Developmental stage, phenotype. and migration distinguish naive- and effector/memory-like CD4-H regulatory T cells. J Exp Med 2004 199 303-313. 

Beyer M, Schultze JL. 2007. CD 4+CD25+high Foxp3+ regulatory T cells in peripheral blood are primarily of effector memory phenotype. J Clin Oncol. 25 2628-2630. 

Newell et al. analyzed human CD8+ T cells through mass cytometry in order to characterize surface biomarkers, cytokines, and antigen specificity with modified peptide-MHC. They have built a panel of 17 cell surface markers of human CD8 + T cells. They have also added nine additional markers six intracellular cytokines, CD107, two cytotoxic granule components, and the perforin and granzyme B. The samples were recollected from six healthy individuals and were stimulated to demonstrate their functional abilities. The analysis was carried out through principal component analysis. This group found that common definitions of naive, central memory, effector memory, and terminal effector subsets correspond to phenotypic clusters in their analysis. Moreover, they have found intermediate phenotypes that connect the clusters to form a continuum, but also exceptional cells that lead the classic definition (44). 

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