Immunoglobulin profile and B-cell frequencies are altered with changes in the cellular micro-environment independent of the stimulation conditions

B-cells are essential in the defense against Mycobacterium tuberculosis. Studies on isolated cells may not accurately reflect the responses that occur in vivo due to the presence of other cells. This study elucidated the influence of microenvironment complexity on B-cell polarisation and function in the context of TB disease. B-cell function was tested in whole blood, PBMCs and as isolated cells. The different fractions were stimulated and the B-cell phenotype and immunoglobulin profiles analysed. The immunoglobulin profile and killer B-cell frequencies varied for each of the investigated sample types, while in an isolated cellular environment, secretion of immunoglobulin isotypes IgA, IgG2 and IgG3 was hampered. The differences in the immunoglobulin profile highlight the importance of cell-cell communication for B-cell activation. In contrast, increased frequencies of killer B-cells were observed following cellular isolation, suggesting a biased shift in augmented immune response in vitro. This suggests that humoral B-cell function and development was impaired likely due to a lack of co-stimulatory signals from other cell types. Thus, B-cell function should ideally be studied in a PBMC or whole blood fraction.