Monocytes with altered phenotypes in posttrauma patients

Posttrauma patients show impaired immune responsiveness and increased susceptibility to infections. Although monocytes in these patients have been known to express decreased HLA-DR, induction of HLA-DR using interferon gamma failed to reduce susceptibility to infection, suggesting additional factors also may be involved in the impaired immune responsiveness. CD4 plays an integral role in most of the functions of HLA-DR. In newborn infants, who have impaired immune responsiveness, we found a concomitant reduction of CD4 on monocytes with decreased HLA-DR expression. Because monocytes in posttrauma patients have not been previously studied for morphology, coexpression of CD4 and HLA-DR, and activity of alpha-naphthyl butyrate esterase, the purpose of this study was to analyze these factors in this population. Monocyte morphology; expression of CD4, CD11b, CD13, CD16, and HLA-DR by 3-color flow cytometry; and analysis of alpha-naphthyl butyrate esterase activity by cytochemical staining were studied in 27 posttrauma patients and 20 control subjects. Monocytes in posttrauma patients showed significant differences in the following characteristics compared with controls: (1) increase of subsets displaying the phenotypes CD4-/CD14+/HLA-DR- and CD4-/CD14+/CD16-, (2) decrease in mean fluorescence intensity of CD4 and HLA-DR expression in monocytes that were positive for these markers, (3) decrease in alpha-naphthyl butyrate esterase activity, and (4) decreased amount of cytoplasm and cytoplasmic vacuoles.Conclusion.-Our study suggests that in posttrauma patients, as in newborns, there is a marked increase of monocytes with decreased expression of CD4 and HLA-DR, as well as decreased alpha-naphthyl butyrate esterase activity. Concomitant reduction in CD4 and HLA-DR expression on monocytes may contribute to impaired immune responsiveness in these patients.