Reactions of peripheral blood mononuclear cells (PBMC) of camels with monoclonal antibodies against ruminant leukocytes

The particular immune system of the camel has been but little investigated. In this work circulating camel peripheral blood mononuclear cells (PBMC) were studied by flow cytometry. Monoclonal antibodies (mAbs) raised against ruminant leukocytes were used for the detection of cell surface antigens. Monoclonals to T-cell markers, CD4 (CACT138A) and CD8 (CACT80C), exhibited no reactivity towards camel PBMC in contrast to their reactivity to PBMC of other ruminant species and those of cattle in particular. A relatively high percentage (29.1 ± 8.9%) of camel PBMC reacted with a non-immunoglobulin cell surface marker, B-132, comparable to the reactivity of bovine PBMC. The B-B7 cell marker revealed 22.4 ± 10.0% of reactive camel PBMC while the CD45 leukocyte common antigen was identified only on 19.4 ± 3.1% of camel PBMC as compared to 74.7 ± 4.9% for bovine PBMC. IgM (PIg45A) was detected on 9.1 ± 1.4% of camel PBMC and on 46.6 ± 19.5% of the bovine PBMC. Double fluorescent labeling with two B-cell markers and an anti-ruminant λ light-chain mAb revealed 7-9% of cells bearing both B and λ L-chain markers. Light chain reactivity was also assessed using an anti-goat F(ab′) ₂ antiserum. The values obtained, 14.3 ± 5.8% for the camel and 47.8 ± 2.7% for the cattle, are close to the values observed for surface IgM. These data suggest that camels, like other ruminants, possess L-chain bearing cells of the B-cell lineage. However, in the camel, Igs are different in that in addition to regular four chain Igs, about 65% of them possess two heavy chain Igs devoid of light chains. Because different sets of V _H gene segments are used by four and two chain Igs, it is possible that there might be two lineages of B-cells each secreting a different form of antibodies.