The regulatory influence of Interleukin 2 (IL-2) on the expression of IL-2 receptors (IL-2R) was studied using long-term cultured T-cell lines and recombinant IL-2 (r-IL-2). Three T-cell lines with different growth requirements were used as model systems: insulin-specific BK-BI-1.2 cells express IL-2R transiently after antigenic restimulation, ovalbumin-reactive BK-OVA-1R cells express IL-2R permanently, and BK-BI-2.6.C6 cells bear IL-2R constitutively but do not exhibit antigen reactivity. All three T-cell lines exhibited the property of increased IL-2R expression in the presence of r-IL-2, as tested by cytofluorometry employing monoclonal antibody AMT-13 directed at the murine IL-2R. IL-2R density was influenced selectively by r-IL-2, because the level of Thy-1.2 molecules was similar in the presence and absence of r-IL-2. With BK-BI-2.6.C6 cells, r-IL-2 was shown to upregulate high-affinity receptors. Since BK-BI-2.6.C6 and BK-OVA-1R cells were grown in the absence of feeder cells, these data show that r-IL-2 can regulate the expression of its own receptor without the participation of monokines. Results obtained with the T-cell line BK-BI-1.2, representing insulin-specific T cells with transient IL-2R expression, show that the presence of r-IL-2 did not prevent a decline in IL-2R density occurring on day 5 after antigenic stimulus. This indicates that additional mechanisms besides antigen- and IL-2-induced IL-2R upregulation are operative in controlling IL-2R density on the cell surface.

To estimate the cellular immune response of workers highly exposed to mixtures of organic solvents, subpopulations of peripheral blood lymphocytes (PBLs) were analyzed. For this, the PBLs of nine floorers (aged 25-58 years, exposure time 8-35 years) were subsequently labelled with monoclonal antibodies OKT4, OKT8, OKT11, anti-Leu 7 and anti-Leu 12. Analysis was made by a FACS IV cell sorter (Becton-Dickinson, USA). The control group consisted of matched pairs of healthy donors. In the exposed group we found a decrease in the OKT11 (all) T cell fraction, a decrease in the OKT4 helper cells, an increase in the anti-Leu 7 positive cells, mostly natural killer cells, an important increase in anti-Leu 12 labelled T cells, i.e., human B-lymphocytes, and no differences in the OKT8 suppressor cells. Total fluorescence intensity profiles between the exposed and the unexposed group did not differ, i.e., the marker density on the cell surfaces remained unchanged. Similar changes in lymphocyte subpopulations are found in states of immunodeficiency and immunogenetic forms of aplastic anemia, a disease whose etiological relationship may be due to long-term exposure to organic solvents.

A monoclonal antibody (CB.1) is described that defines a new triggering signal for human cytotoxic T lymphocytes (CTL). The antibody precipitates a 103-kDa surface antigen from activated normal human T cells. The antigen is undetectable or present in only low amounts on resting T lymphocytes but its expression increases strongly after activation and proliferation on T4+ and T8+ T lymphocytes. Binding of antibody CB.1 to CTL results in triggering of the lethal hit. This induction of cytotoxicity is dependent on cross-linking of CTL and an Fc receptor-bearing target cell with CB.1 and requires Ca2+ like antigen-specific triggering. CB.1-induced triggering can be specifically inhibited by binding of antibodies to the T8 or T4 molecules on T8+ or T4+ CTL.