Blastogenic responses, interleukin-2 production and interleukin-2 receptor expression on CD4+ and CD8+ lymphocytes in rhesus monkeys experimentally inoculated with Loa loa.

Abstract

To better understand cellular responses in loiasis infection, in vitro blastogenesis of peripheral blood mononuclear cells (PBMC) to filarial antigen was assessed in 12 Loa loa-inoculated rhesus monkeys over a two-year period. Cellular reactivity to antigen was observed between 10-35 weeks postinoculation (WPI), but had declined by week 50. The roles of interleukin-2 (IL-2) and IL-2 receptor (IL-2R) expression of CD4+ and CD8+ T cells in regulating the response to antigen were examined during the initial (57 WPI) and late (92 WPI) time points of the observed diminished reactivity to antigen. The levels of IL-2 in antigen cultures at both time points were not significantly different from those in unstimulated cultures. Also, exogenous IL-2 partially reversed the PBMC response to antigen. The percentages of CD4+ and CD8+ T cells expressing IL-2R in antigen cultures at 57 WPI were not different from those of control animals. Likewise at 92 WPI, the percentage of CD4+ T cells expressing IL-2R in antigen cultures, were not increased above those of control animals. In contrast, the percentage of CD8+ T cells expressing IL-2R in antigen cultures were significantly increased above those of control animals (P < 0.0001), coinciding with an increase in CD8+ T cells numbers in these cultures. The data show that factors besides IL-2; and probably an imbalance in the percentages of CD4+ and CD8+ T cells bearing IL-2R in antigen cultures, may contribute to the diminished reactivity to antigen in L. loa-inoculated rhesus monkeys.