THE ABILITY OF PERIPHERAL-BLOOD MONONUCLEAR-CELLS OF RABBITS INFECTEDWITH TREPONEMA-PALLIDUM TO PRODUCE IL-2

It was previously found that the cell-mediated immune response involve d in protection against Treponema pallidum is distinctly suppressed du ring some periods in the course of syphilis infection in rabbits. This may be a result of the weak ability of cells to produce Interleukin-2 (IL-2) as well as of IL-2 absorption. The ability of peripheral blood mononuclear cells (PBMC) of syphilitic rabbits to produce IL-2 develo ps within the first two weeks after infection reaching a maximum in ab out the eleventh week. In infection of longer duration, this capabilit y was distinctly lowered. This low level of activity (no higher than i n PBMC of normal rabbits) was maintained for 31 weeks. The ability of PBMC to absorb IL-2, in parallel with its production, was found at the same time in the course of syphilis infection (7-11 weeks). In long-l asting syphilis (more than 12 weeks) both abilities seem to be inhibit ed. Sera of syphilitic rabbits were found to have a higher level of IL -2 inhibitor than those of normal rabbits. Only in syphilis lasting 9 to 11 weeks, when the production of IL-2 was the greatest, was the lev el of IL-2 inhibitor nearly the same as in normal rabbit sers. In syph ilis lasting longer, the increased level of inhibitor was accompanied by a decreased ability of cells to produce IL-2. These findings sugges t that IL-2 inhibitor may be bound to IL-2 or IL-2 receptor on T lymph ocytes and in this way would leat to weakening of T cell function and resistance against Treponema palidum infection.