Background: This study was designed to improve identification of human blood monocytes by using antibodies to molecules that occur consistently on all stages of monocyte development and differentiation.Methods: We examined blood samples from 200 healthy adults without clinically diagnosed immunological abnormalities by flow cytometry (FCM) with multiple combinations of antibodies and with a hematology analyzer (Beckman LH750).Results: CD91 (a 2 -macroglobulin receptor) was expressed only by monocytes and to a consistent level among subjects [mean median fluorescence intensity (MFI) 5 16.2 6 3.2]. Notably, only 85.7 6 5.82% of the CD91 1 monocytes expressed high levels of the classical monocyte marker CD14, with some CD91 1 CD16 1 cells having negligible CD14, indicating that substantial FCM under-counts will occur when monocytes are identified by high CD14. CD33 (receptor for sialyl conjugates) was co-expressed with CD91 on monocytes but CD33 expression varied by nearly ten-fold among subjects (mean MFI 5 17.4 6 7.7). In comparison to FCM analyses, the hematology analyzer systematically over-counted monocytes and eosinophils while lymphocyte and neutrophil differential values generally agreed with FCM methods.Conclusions: CD91 is a better marker to identify monocytes than CD14 or CD33. Furthermore, FCM (with anti-CD91) identifies monocytes better than a currently used clinical CBC instrument. Use of anti-CD91 together with anti-CD14 and anti-CD16 supports the identification of the diagnostically significant monocyte populations with variable expression of CD14 and CD16.
Background-Subsets of human blood monocytes can be defined by CD14 and CD16 expression but otherwise are often assumed to be relatively homogeneous. However, we observed unexpected heterogeneity in other properties of monocytes from healthy adults without clinical immunological abnormalities.
The efficacy of a novel synthetic antimicrobial peptide (WLBU2) was evaluated against three oral microorganisms (grown planktonically): Streptococcus gordonii, Fusobacterium nucleatum, and Porphyromonas gingivalis. WLBU2 killed all three species, with F. nucleatum being the most susceptible. WLBU2 also reduced the bacterial burden of S. gordonii and F. nucleatum biofilms.
Routinely, human natural killer (NK) lymphocytes are identified as CD3eneg CD56bright or dim. CD3neg CD56neg cells with low perforin are found in viremic patients infected with human immunodeficiency virus and hepatitis C virus (reviewed, N.K. Bjorkstorm et al., Trends Immunol. 31:401, 2010). To our surprise, we found by flow cytometry that CD3neg perforin(PRF1) positive NK cells included as many as 50% CD56neg cells within the blood of 97 healthy subjects. Among these subjects (aged 21 to 62 years), the CD3eneg PRF1positive cells included at least 10% CD56neg cells in 24 of 97 (~25%) subjects. CD56neg perforin high CD3neg cells were over 50 cells/mm3 of blood in 14% of the healthy donors. As anticipated, the CD56dim cells had ~7 fold higher perforin MFI than the CD56bright cells. Notably in the healthy donors with high frequencies of CD56neg cells, these cells had bimodal perforin levels comparable to the levels in the CD56bright and CD56dim subsets. The perforin levels indicate that many CD56neg NK cells may have strong cytotoxicity in healthy donors in contrast to the low perforin and cytotoxicity observed in CD56neg NK cells of the viremic patients. We conclude that CD56neg NK cells now warrant attention as potential cytotoxic cells after receiving considerable attention as high chemokine-secreting cells.
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