Dromedary camel CD14high MHCIIhigh monocytes display inflammatory properties and are reduced in newborn camel calves

Abstract

Background:In human and different animal species, blood monocytes are classified based on their expression pattern of different monocytic markers into phenotypically and functionally different subsets. In the current study, we used flow cytometry and monoclonal antibodies to CD172a, CD14, CD163 and MHCII to identify monocyte subsets in peripheral blood of dromedary camels. Results: Based on CD14, CD163 and MHCII expression, camel CD172a + monocytes were divided into three subsets: The major subpopulation of camel monocytes (mo-I) showed high expression of CD14 and CD163, but low expression of MHCII. A second subset of monocytes (mo-II) expressed highly all three markers, CD14, CD163 and MHCII. A third monocyte subset (mo-III) displayed low expression of CD14 and CD163 with high MHCII expression. While the two MHCII high subsets (mo-II and mo-III) showed higher expression of CD11a in comparison to the MHCII low subset (mo-I), CD18 and CD11b were highest expressed on the two CD14 high subsets (mo-I and mo-II). Bacterial stimulation of camel leukocytes identified mo-II cells as an antimicrobial monocyte subset with the highest phagocytic and ROS production capacity. The comparison of monocyte counts and phenotype between newborn calves and adult camels revealed significantly reduced numbers of mo-II cells in newborn animals. Monocytes of newborns expressed significantly more CD172a and CD163 molecules but less CD14 and MHCII molecules than monocytes of adult camels. Conclusions: Camel monocyte subsets, mo-I, mo-II and mo-III are counterparts of bovine classical, intermediate and non-classical monocytes respectively. The distribution of camel monocyte subsets is influenced by age.

Recent Advances in Camel Immunology

“… MHC, Major Histocompatibility Complex; WSU, Washington State University; BD, Becton Dickinson; mIgM, mouse immunoglobulin M; mIgG, mouse immunoglobulin G; gIgG, goat IgG ( 36 , 59 , 61 , 85 , 86 ). …”

“…Due to the lack of monoclonal antibodies cross-reactive with camel CD16 ( 59 ), three subpopulations of monocytes in dromedary camels have recently been identified based on the expression profiles of CD172a, CD14, MHCII, and CD163 ( 61 ). Similar to the porcine and bovine systems ( 104 , 106 , 110 – 112 ), the signal-regulatory protein alpha (CD172a) has been identified as a pan monocyte marker for camel monocytes.…”

“…A small fraction of camel monocytes (6 % of total monocytes) expresses high levels of CD14, CD163, and MHCII (CD14 high CD163 high MHCII high ) and is designated as cMo-II. The third minor monocyte subpopulation cMo-III (5 % of total monocytes) displays high expression of MHCII but low expression of CD14 and CD163 (CD14 low CD163 low MHCII high ) ( 61 ) ( Figure 2 ).…”

“…Monocytes from newborn and adult camels showed different expression patterns of the monocyte-related surface molecules, CD172a, CD14, CD163 and MHCII ( 61 ) ( Figure 4 ). Compared to adult camels, newborns display higher numbers of cMo-I and cMo-III, and less numbers of inflammatory cMo-II ( 61 ).…”

Changes in Cell Vitality, Phenotype, and Function of Dromedary Camel Leukocytes After Whole Blood Exposure to Heat Stress in vitro

“…Recent studies in camel immunology have enabled the characterization of several subpopulations of camel leukocytes, including camel monocyte subsets, some subsets of camel lymphocytes, and camel neutrophilic granulocytes (12)(13)(14)(15)(16)(17)(18). Neutrophils and monocytes are circulating myeloid immune cells with key roles in innate immunity to bacterial infections.…”