The CD14⁺CD16⁺ monocytes in erysipelas are expanded and show reduced cytokine production

In human peripheral blood the classical CD14⁺⁺DR⁺ monocytes and the pro-inflammatory CD14⁺CD16⁺DR⁺⁺ monocytes can be distinguished. In erysipelas we found strongly increased numbers of CD14⁺CD16⁺ monocytes on the day of diagnosis (day 1) in 11 patients with an average of 150.5±76.0 cells/μl, while 1 patient had low levels (35 cells/μl, control donors 48.8±19.8 cells/μl). The classical monocytes were only moderately elevated in the erysipelas patients (factor 1.7 as compared to controls). Patients exhibited increased body temperature, erythrocyte sedimentation rate and increased serum levels for C-reactive protein (CRP), IL-6 and macrophage-colony-stimulating factor. Among these, body temperature and CRP showed a significant correlation to the numbers of CD14⁺CD16⁺ monocytes. In 4 of 4 patients with high levels of CD14⁺CD16⁺ monocytes, these levels returned to that seen in controls by day 5 of antibiotic therapy. Determination of intracellular TNF was performed by three-color immunofluorescence and flow cytometry after ex vivo stimulation with lipoteichoic acid, a typical constituent of streptococci. Here, patient CD14⁺DR⁺⁺ pro-inflammatory monocytes showed a twofold lower level of intracellular TNF. By contrast, expression of TNF was unaltered in the classical CD14⁺⁺ monocytes. These data show that in erysipelas the pro-inflammatory CD14⁺CD16⁺DR⁺⁺ monocytes are substantially expanded and selectively tolerant to stimulation by streptococcal products.