Identification of putative B1 B-cells in cows

Natural antibodies (Nabs) are antibodies spontaneously produced by B1 B-cells, without prior antigenic stimulation and are considered part of the innate immune system. They are primarily of the IgM isotype and are often directed to conserved microbial components. In contrast, specific antibodies (Spabs) are produced by B2 B-cells that do need antigenic specific stimulation to induce antibody production. Nabs levels might be related with disease resistance in dairy cows. However, defining the exact contribution of natural and specific antibodies is difficult, because they cannot be easily discriminated in serum. We therefore tried to identify the Nabs-producing bovine B1 B-cells. This will enable us to determine the relationship of these cells with disease resistance of dairy cows. Peripheral blood mononuclear cells (PBMCs) of cows were tested by flow cytometry for markers and functional characteristics of B1 B cells, described earlier for B1 B cells in other species. The combination of one extracellular and one intracellular marker stained a population with characteristics of B1 B cells. Additionally experiments are performed on FACS sorted cells to confirm these results.