The inflammatory cytokines in measles: Correlation between serum interferon-γ levels and lymphocyte subpopulations

Interleukin-1 (IL-1β), tumour necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) were measured in serum from children with measles using an immunoradiometric assay. The IFN-γ level was increased in 52 out of 54 patients in the acute phase of measles (<7 days of illness), and then declined to an undetectable level in the convalescent phase. Neither IL-1 nor TNF could be detected during the course of the illness. The mean serum IFN-γ level was at its peak on day 4 and could be detected over a 7-day period after the onset of fever, coinciding with the febrile period (6.9±1.5 days). In the acute phase, the phytohaemagglutinin responses, absolute number of platelets, total lymphocyte counts, CD3⁺, CD4⁺, CD8⁺ cell counts and the CD4/8 ratio were depressed, while stab cell number and lactate dehydrogenase levels were higher than those in the convalescent phase. Using Spearman rank sum test, the IFN-γ level was correlated negatively with the peripheral lymphocyte (P<0.01), CD3⁺ (P<0.05), CD4⁺ (P<0.05) cell counts and the CD4/8 ratio (P<0.05) and correlated positively with the stab cell count (P<0.01) but not with any other parameter. When the acute phase findings were compared between 28 complicated and 40 uncomplicated patients, the former were younger (P<0.01) and had higher maximum body temperature during the illness (P<0.05) than the latter, there was no difference in their IFN-γ levels. These results show that endogenous IFN-γ appears in the circulation during the acute febrile phase of measles, but does not contribute directly to any complication of the disease.