Arginine supplementation enhances mitogen-induced splenocyte proliferation but does not affect in vivo indicators of antigen-specific immunity in mice.

Arginine is a conditionally essential amino acid with many physiologic roles. Its role in immune function has been one of major focus with conflicting results. Early in vitro immune studies demonstrated increased mitogen-induced lymphocyte proliferation with dietary arginine supplementation; however, not all studies confirmed this effect. Even less is known about the effect of arginine supplementation on in vivo immune responses. To test whether arginine supplementation enhances in vivo indicators of immune function, young female BALB/c mice were fed either the AIN-93G rodent diet (6.4 g arginine/kg diet) or the same diet with 20 g total arginine/kg diet for 15 d before delayed-type hypersensitivity (DTH) testing with 2,4-dinitrofluorobenzene (n = 16-18/diet group). The same mice were challenged with influenza virus A/Port Chalmers/1/73 (H3N2) 15 d later. Mice were killed 3, 6, or 31 d postinfluenza challenge (5-6/diet group on each day). Mitogen-induced splenocyte proliferation, body weight, anti-influenza serum antibody, lung viral titers, and serum arginine were measured. DTH did not differ between diet groups. On d 6 and 31 postchallenge, mitogen-induced proliferation of splenocytes from mice fed the arginine diet was >1.5-fold that of mice fed the control diet (P < 0.05). Body weight and influenza lung viral and serum antibody titers did not differ between diet groups. These data suggest that despite significant enhancement of in vitro mitogen-induced splenocyte proliferation, arginine supplementation does not have a biologically significant effect on antigen-specific in vivo indicators of immune function in this model.