Regulation of nitric oxide production by cytokines in human macrophages: <span style="font-size:12.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";mso-ansi-language:EN-IN;mso-fareast-language: EN-IN;mso-bidi-language:HI">Possible role in <i>P. vivax </i>malaria</span>

Abstract

Production of reactive nitrogen intermediates (RNI) by macrophages in response to the malaria antigen of <i>P. vivax </i>and various cytokines was evaluated. Live malaria antigens, interferon-γ, concanavalin A, interleukin-6 and tumour necrosis factor-α induced production of RNI in a dose dependent manner. RNI production was found to be steadily increased for a period of 72 hr and it was further enhanced when the live malaria antigen was co-incubated with interleukin-6 and interferon-γ and/or tumour necrosis factor-α. L-N-monomethyl arginine (L-NMA) and polymyxin B were found to inhibit the production of RNI. Production of RNI by cAMP however, was not inhibited by polymyxin B. Dead parasites (heated) did not affect the production of RNI. Our results are thus consistent with the possibility that cytokines may contribute to the pathology of the host cells and also to the parasite immunosuppression through the production of the reactive nitrogen intermediates.