Exploratory assessment of CD4+ T lymphocytes in brown hares (Lepus europeus) using a cross-reactive anti-rabbit CD4 antibody

In lagomorphs, lymphocyte subset distributions and the importance of CD4+ T cell levels has so far only been considered in the frame of rabbit disease models. In this study, the first assessment of CD4+ T lymphocytes in peripheral blood cells in brown hares (Lepus europaeus L., 1758), a further leporid species using a cross-reactive rabbit anti-CD4 antibody in flow cytometry, is presented. In addition, the entire coding region of the hare CD4 gene (1380 bp) coding for a polypeptide of 459 amino acids has been sequenced. Using generalized least squares fitting by maximum likelihood (GLS) test, significantly (p = 0.0095) higher CD4+ T cell frequencies in males than in females and significantly (p = 0.0001) higher frequencies for leverets (younger than 2 months of age) than for subadult and adult (older than 7 months of age) individuals were detected. No significant age influence, however, was found for subadult and adult hares. The study is particularly meant to provide a first step in establishing a toolbox for the assessment of the immune response in this leporid species.