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

Rationale: 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.

Methods: 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).

Results: 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.

Conclusions: 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.