Preliminary findings on the absence of PEPITEM release in B cells isolated from Saudi donors: implications for expanded population studies.

Background: Adiponectin (AQ) plays a role in regulating immune responses. Previous research indicates that B cells can affect T cell transmigration via the adiponectin-induced peptide PEPITEM in Caucasians. This study explores whether this mechanism is also applicable to Saudi populations, considering potential ethnic variations in immune response.

Methods: We conducted unbiased peptidomic screen on B cells, NK cells, and monocytes isolated from the peripheral blood of male healthy Saudi donors. The cells were stimulated with AQ, and the secretion of PEPITEM and other peptides was assessed using liquid chromatography-mass spectrometry (LC-MS/MS). Flow cytometry was utilized to confirm the purity of isolated cell populations and to verify the expression of adiponectin receptors AR1 and AR2.

Results: PEPITEM was not detected in the supernatants of AQ-stimulated B cells, NK cells, or monocytes. All three cell populations were isolated and purified with high purity, confirmed by flow cytometry showing AR1 and AR2 expression on the surface of these cells. Specifically, less than 47% of B cells expressed ARs, with AR1 at 12% and AR2 at 17%. AQ stimulation increased the number of identified peptides in B cells and monocytes but decreased peptide numbers in NK cells. Dimensionality reduction analysis demonstrated clear segregation of cell types, with strong reproducibility across technical replicates.

Conclusion: The inability of B cells to release PEPITEM in response to AQ stimulation is an interesting finding and it needs more confirmatory tests and experiments, however; a hypothesis about the impact of predisposing factors, such as ethnicity could be formulated and tested in the future.