Cytokine mRNA expression in leprosy: a possible role for interferon-gamma and interleukin-12 in reactions (RR and ENL)

Leprosy patients during the natural course of the disease may develop react ional episodes, namely reversal reaction (RR) and erythema nodosum leprosum (ENL). Immunological events described as occurring during RR indicate up-r egulation of the immune response, whereas in ENL the events are not fully u nderstood The aim of this study was to analyse the in vivo pattern of cytok ine gene expression in the reactional states of leprosy. Peripheral blood m ononuclear cells (PBMC, n=14) and tissue samples (n=17) obtained from patie nts with ENL and RR were obtained and assayed by RT-PCR. PBMC obtained from unreactional patients (n = 15) and normal individuals (n = 5) were also as sessed. Expression of interferon (IFN)gamma, granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin (IL)-2Rp55, perforin and IL-1 beta mRNA in PBMC were detected mostly in ENL/RR patients, but not in unreactio nal patients. Likewise, cytokines such as IL-6, IL-8, tumour necrosis facto r (TNF)alpha and TNF beta were also present in reactional and tuberculoid p atients as opposed to lepromatous leprosy (BL/LL). Interestingly, the major ity of ENL/RR patients showed messages for IL-6, IL-10, IL-12 and TNF alpha in the skin. IFN gamma was detected in 84.6% (ENL) and 100% (RR) of the pa tients, whereas IL-4 was detected only in few individuals (38.5 and 25%, re spectively). Although mRNA expression and protein levels may be different, the data reported in this study suggest a cytokine mRNA profile that seems to be indistinguishable for RR and ENL. In addition, it shows up-regulation of immunoinflammatory cytokines in the blood and tissue of the same patien t examined before and during reaction. Furthermore, it is suggested that th is pattern of response results from an immunological reactivation that migh t lead to an acute inflammatory response in both reactional episodes.