Lymphocyte subsets in HTLV-II-infected former blood donors: Relationship to spontaneous lymphocyte proliferation

Abstract

Previous studies showed that over 70% of HTLV-seropositive blood donors from the Los Angeles area are infected with HTLV-II; further, mononuclear cells from about half of these HTLV-II + donors exhibit spontaneous lymphocyte proliferation (SLP) during in vitro culture. To determine if HTLV-II +SLP + donors exhibit more marked immune system changes than HTLV-II +SLP − donors, lymphocyte subsets for these two HTLV-II + groups were compared to an uninfected control group. The percentage of lymphocytes expressing CD3 was significantly increased and the percentage expressing a CD16/56 +CD3 − phenotype (natural killer cells) was significantly decreased in the HTLV-II +SLP + group ( N = 34) versus the control group ( N = 49). On the basis of absolute numbers, the lymphocyte number was significantly higher in the HTLV-II +SLP + group than in the control group and reflected significant increases in the numbers of both CD4 and CD8 subsets of T cells. Analysis of proportional changes in CD4 and CD8 cell subsets revealed significant increases in the proportions of CD4 cells expressing HLA-DR, CD8 cells expressing HLA-DR, and CD8 cells expressing CD45RO for the HTLV-II +SLP + group versus the control group. For all phenotypic parameters measured, no significant differences were noted when comparing the HTLV-II +SLP − group ( N = 21) and the control group. Cell culture experiments utilizing purified CD4 cells and CD8 cells from a subsets of each study group revealed that in vitro spontaneous proliferative capacity resides within both the CD4 cell and CD8 cell populations from SLP + individuals. These findings show that changes in circulating lymphocyte subsets in HTLV-II infection are found only in association with SLP, and that the capacity to exhibit SLP characterizes both CD4 and CD8 lymphocyte subsets.