To examine the immunopharmacological actions of an extract isolated from inflamed skin of rabbits inoculated with Vaccinia virus (
Neurotropin), its effect on the immune responses in aging BALB/c mice was examined.
Neurotropin clearly restored the decreasing T-cell-dependent immune responses such as delayed-type
hypersensitivity (DTH) response and plaque-forming cells (PFC) response to sheep red blood cells (SRBC) when administered i.p. from 13 months old (mo) to 16 mo. However,
Neurotropin administration from 2 to 5 mo had no effect on the immune responses of young animals.
Neurotropin administration from 13 to 16 mo restored not only the T-cell proliferation of spleen cells induced by
concanavalin A (Con A) and
phytohemagglutinin (PHA), but also the
interleukin-2 (IL-2) production by spleen cells activated with Con A. However,
Neurotropin did not affect the responsiveness of Con A-activated spleen cells to exogenous recombinant
IL-2. An absence of suppressor cells capable of inhibiting the
IL-2 production in the spleens was confirmed in the 16 mo mice.
Neurotropin administration also restored
IL-1 production by peritoneal macrophages stimulated with
lipopolysaccharide (LPS). These results suggest that long-term administration of
Neurotropin restores the decreasing T-cell-dependent immune responses through the recovery of
IL-2 and in part
IL-1 production, but not the responsiveness to
IL-2 in aging BALB/c mice.