Low molecular weight human T-cell response immunopotentiator: alpha-2'-deoxy-3-deazaguanosine.

We have examined the immunological activity of a unique alpha-nucleoside analog of 2'-deoxyguanosine in which the pyrimidine ring nitrogen in the 3 position is replaced by CH [6-amino-1, 5-dihydro-1-(2-deoxy-alpha-D-erythro-pentofuranosyl)imidazo[4,4-c] pyridin-4-one, alpha-d3DGuo, 1] and its structural analogs. The alpha-d3DGuo is not mitogenic to human PBL. It displayed consistently, however, a potent immunoenhancing activity on PHA-induced human lymphocyte proliferation at concentrations ranging from 0.0125 mM to 0.4 mM in a dose dependent manner. These findings thus suggest that mitogenicity is not a pre-requisite for the immunoenhancing effect. The maximal potentiating effect of alpha-d3DGuo is usually exerted at the bottom range of the dose response to PHA. The magnitude of increase is about the same as that mediated by rIL-2. Similarly, Con A mediated lymphocyte proliferation is markedly enhanced by alpha-d3DGuo. When added during allogeneic MLR, alpha-d3DGuo also augmented the proliferation of alloreactive T-cells and the magnitude of response was similar to that induced by rIL-2. The alpha-d3DGuo induced increase in allogeneic response was dependent on concentrations of both alpha-3dDGuo and alloantigens as noted with T-mitogen induced proliferative responses. The cytotoxic activity of lymphocytes induced in allogeneic mixed cultures was also augmented by alpha-d3DGuo. It showed, however, no potentiating effect on B-lymphocytes proliferation stimulated either with SAC or PWM. The alpha-d3DGuo is also able to restore, at least partially, the depressed proliferative responses of T-cells to both PHA and Con A.(ABSTRACT TRUNCATED AT 250 WORDS)