Lymphocyte subpopulations in Bancroftian filariasis: activated (DR+) CD8+ T cells in patients with chronic lymphatic obstruction.

To examine the relationship between lymphocyte phenotypes and states of activation in patients with Bancroftian filariasis, dual colour flow cytometry and concurrent in vitro cell culture were performed on normal individuals (NV; n = 15), and on patients with either asymptomatic microfilaraemia (MF; n = 12) or elephantiasis (CP; n = 11). In contrast to findings by others in a population with Brugian filariasis, the percentages of total B lymphocytes (CD19), T lymphocytes (CD3), helper/inducer T lymphocytes (CD4), and suppressor/cytotoxic T lymphocytes (CD8) in both patient groups were found to be within the range defined by clinically normal individuals. Furthermore, there were no differences among the groups in the expression of the IL-2 receptor (CD25) on T cells. There was, however, a significantly greater proportion (P less than 0.01) of 'activated' cytotoxic/suppressor lymphocytes (defined by co-expression of CD8 and HLA-DR) in patients with elephantiasis (16.4 +/- 8.6%) than in the MF (8.9 +/- 2.6%) or NV (8.3 +/- 2.9%) groups. Further, when the expression of this activation antigen was examined in parallel with in vitro mitogen responsiveness, an inverse correlation between the percentage of CD8+ HLA-DR+ lymphocytes and pokeweed mitogen-induced proliferation was seen (r = -0.54; P less than 0.001). These data provide further definition of the immunoregulatory abnormalities seen in human filarial infections and suggest that activated CD8+ T lymphocytes may be involved in the pathogenesis of the chronic obstructed lymphatic form of this disease.