Leukocyte populations and their cell adhesion molecules expression in newborn dromedary camel calves

Abstract

Background and aim: Different properties of the newborn immune system have been characterized in many species. For the newborn camel calf, however, the phenotype and composition of blood leukocytes have so far not been evaluated. The current study aimed to analyze the distribution of leukocyte subpopulations and their expression pattern of cell adhesion molecules in newborn and adult dromedary camels.

Materials and methods: Blood samples were collected from 17 newborn camel calves and 32 adult camels. For each sample, total leukocytes were separated and analyzed for their composition and cell adhesion molecules expression by flow cytometry.

Results: In comparison to adult camels, newborn camel calves had higher leukocyte numbers and higher numbers of neutrophils, monocytes, and lymphocytes but lower numbers of eosinophils in their blood. Among the lymphocyte populations in calves, the fractions of B cells and γ^δ T cells were elevated when compared to adults, whereas CD4-positive T cells were reduced. The comparison between camel calves and adult camels revealed significantly lower expression of the cell adhesion molecules CD11a, CD11b, and CD18 on granulocytes, monocytes, and lymphocytes in calves.

Conclusion: Newborn camel calves show a distinct composition and phenotype pattern of blood leukocytes when compared to adult camels. The observed rise in many leukocyte populations in calf blood may be due to reduced migratory activity in calf leukocyte populations.

Keywords: adhesion molecules; flow cytometry; immunophenotype; leukocytes; newborn camel calf.

Figure-1

Gating strategy for the identification of the main leukocyte populations in the peripheral blood of newborn camel calves. (a) In a side scatter (SSC)/forward scatter (FSC) dot plot, camel granulocytes (G), monocytes (M), and lymphocytes (L) were gated according to their FSC and SSC characteristics. After setting a gate on granulocytes, eosinophils (E) and neutrophils (N) were identified according to their different autofluorescence intensities in the FL1 fluorescence channel. (b) For each leukocyte subpopulation, the mean SSC and FSC values were calculated and presented comparatively for newborn and adults (*p<0.05).

Figure-2

Total and differential cell count of camel blood leukocytes. (a) Total leukocyte count and numbers of neutrophils, eosinophils, lymphocytes, and monocytes in the blood of newborn and adult camels are presented as means±SEM (*p<0.05).

Figure-3

Adhesion molecules expression on leukocyte populations in blood of newborn and adult camels. The differential expression densities of the cell adhesion molecules CD11a, CD11b, and CD18 were estimated as the mean fluorescence intensity of each molecule on the surface of blood neutrophils, lymphocytes, and monocytes. Data for calves and adults were presented graphically (*p<0.05).

Figure-4

The relative composition of blood lymphocytes in the peripheral blood of newborn and adult camels. (a) After setting a gate on lymphocytes in a SSC/FSC dot plot, the percentages of γ^δ T cells, CD4-positive T helper cells, and B cells under total lymphocytes were estimated in separate dot plots according to their staining with the cell-specific marker. (b) Data for newborn and adult camels were presented as mean±SEM (*p<0.05).