Impaired Semaphorin 4C (Sema4C) Induction In Patients With Common Variable Immunodeficiency (CVID)

Semaphorins have been identified as having key roles in immune regulation. Our laboratory has previously reported that Sema4C is inducible in human B-cells and may be important for CD27+memory B-cell development and formation of immune synapse. Our aim was to determine if Sema4C expression was impaired in CVID subjects. 15 CVID subjects and 18 healthy controls were recruited as part of C-PRIMES registry. A blood sample was collected and PBMC were isolated. Cells were either cytospun immediately or grown in slide chambers for 5 days in complete medium with anti-CD40±IL-4±IL-21. Sema4C expression and colocalization with B-cell receptor (BCR) was determined by confocal microscopy. Sema4C mRNA expression relative to GAPDH housekeeping gene was performed by RT-qPCR. Statistical analyses were performed by Mann-Whitney test (p value < 0.05 was considered statistically significant). At baseline, Sema4C mRNA expression was significantly lower in CVID compared to controls (p<0.05). Upon 5 days stimulation with anti-CD40+IL-4+IL-21, PBMCs from controls demonstrated increased Sema4C protein expression and formation of a polarized synapse in association with BCR on confocal microscopy. In contrast, CVID subjects showed membranous expression of Sema4C protein, with little co-localization with BCR, and without polarized synapse formation. We have determined that this group of CVID subjects have impaired Sema4C expression/induction, a molecule that may be important for CD27+memory B-cell development and formation of immune synapse upon IL-21 in vitro stimulation. Further studies will be required to determine if impaired Sema4C expression may play a role in decrease immunoglobulin production observed in CVID.