Background/Purpose Semaphorin3A (sem3A) is an important regulatory molecule, previously reported to play a role in the pathogenesis of rheumatoid arthritis and later by us in lupus glomerulonephritis. In addition, sema3A was shown to be a marker of T regulatory cells. A subpopulation of B cells, namely B regulatory cells (Bregs), was recently identified by us as CD19+CD25highIL-10highTGF-βhigh, and demonstrated to be of high sema3A expression.
We therefore asked whether serum levels of sema3A is altered in SLE patients, whether sema3A expression on B regs of these patients is different, and finally, whether the addition of soluble sema3A to cultured B cells improves their regulatory and or pro-inflammatory properties.
Materials and Methods Serum from SLE patients, RA patients (disease control) and normal controls was analysed for sema3A levels and was correlated with clinical parameters of SLE. The expression of sema3A on Bregs was compared between SLE patients and normal individuals. In addition to this, the expression of CD72 and TGF-β (inhibitory molecules), and TLR-9 in B cells were assessed in both groups following the addition of recombinant sema3A to cultured B cells.
Results 1. Serum sema3A levels were significantly lower in SLE patients comparing to that of RA patients and much lower than in normal controls (55.04 ± 16.30 ng/ml versus 65.54 ± 14.82 ng/ml, versus 74.41 ± 17.60 ng/ml, respectively, P < 0.0001). 2. Sema3A levels were inversely correlated with SLE disease severity, kidney involvement and anti-cardiolipin-ab. 3. Sema3A expression on Bregs was significantly lower in SLE patients comparing normal individuals (52.2 ± 5.8% versus 82.6 ± 6.4%, P < 0.0001, respectively). 4. The expression of both CD72 and TGF-β was significantly decreased (37.88%, 8.6% respectively) in Bregs of SLE patients versus that on normal Bregs (49.26%, 14.74%, respectively; P = 0.001). However, following the addition of sema3A to cultured B cells, a significant increase of TGF- β and CD72 was noticed (altered in SLE patients, when compared to that of normal individuals). 5. The addition of sema3A to CpG-ODN stimulated B cells from SLE patients reduced TLR-9 expression by almost 50%.
Conclusions 1. This is the first study where sema3A is shown to be altered in both serum and on Breg cells of SLE patients. 2. Sema3A enhances the regulatory properties of Bregs, but this effect is shown to be altered in SLE. 3. Sema3A should be considered a future therapeutic tool in SLE.