Analysis of Ly-6.2-bearing murine lymphocyte subpopulations in relation to the T-lymphocyte markers, Thy-1, Lyt-1, and Lyt-2

CD4+ and CD8+ circulating alpha/beta T-cell repertoires are equally complex and are characterized by different levels of steady-state TCR expression

The repertoire complexity of CD4+ and CD8+ T cells was measured in three healthy blood donors for a number of TCR BV gene families by TCR spectratyping. This method subdivides V family-specific PCR products based on CDR3 length. Genomic DNA was analyzed to determine the distribution of the cells bearing particular V-J rearrangements. cDNA was analyzed to measure the levels of transcripts arising from those same cells. The complexity and distribution of T cells in each lineage were equal for most BV families. Certain families showed frequent skewing in CD8 cells. Analysis of the intensity profiles of RNA versus DNA spectratypes indicated that in general, there is a constant ratio of transcript per cell for all rearranged sizes within a particular family. This ratio appeared higher in CD4 cells. Thus, steady state levels of TCR mRNA were measured and found to be higher in CD4+ than in CD8+ cells.

Modulation and biological effects of Ly-6.2 expression on EL4 tumour cells

EL4 tumour cells maintained in culture were separated by FACS analysis to Ly-6.2 negative and Ly-6.2 positive subsets. The Ly-6.2 negative subset gained expression of this determinant on repeated in vivo passage in C57BL/6 mice. Both subsets injected intraperitoneally or intramuscularly in syngeneic mice induced identical changes in lymphocyte profiles. There was generalised lymphocytolysis in both T- and B-cell compartments. The Lyt-1+, 2- T-lymphocytes were more susceptible to cytolysis causing an alteration of the proportional representation of the Lyt-2+ subset from 30% of splenic T-cells (in normal mice) to over 90% of remaining T-lymphocytes in tumour bearing mice. There was thymic regression in both groups of mice with a resultant thymocyte population expressing the range of phenotypes of mature medullary cells. In spite of similar rates of growth both in vivo and in vitro and identical effects on the lymphoid system the Ly-6.2 negative and Ly-6.2 positive tumour subsets were different in their metastatic potential. Mice injected intramuscularly with either subset had enlarged spleens by the second week of tumour growth caused largely by the accumulation of Ig, Lyt-1 and Thy-1 negative cells. Tumour cells were present only in the group injected with the Ly-6.2+ subset. These mice died of their tumour load a week earlier than those injected with the Ly-6.2- tumour cells.

Positive selection of mouse B and T lymphocytes and analysis of isolated populations by flow cytometry

Mouse spleen cells were separated into Ig+ and Ig- populations by positive selection using petri plates coated with rabbit anti-mouse immunoglobulin. The Ig- cells were subsequently incubated with mouse monoclonal alloantisera to Thy1.2 prior to a second positive selection. The adherent populations were characterized as B (Ig+) or T (Thy1.2+) lymphocytes on the basis of surface immunofluorescence and mitogen-induced proliferation. Analysis of the 2 isolated populations by flow cytometry showed that B and T lymphocytes could be distinguished by their forward light scatter as well as their fluorescence after incubation with fluorescein diacetate.