Human IgMhiCD300a+ B Cells Are Circulating Marginal Zone Memory B Cells That Respond to Pneumococcal Polysaccharides and Their Frequency Is Decreased in People Living with HIV.

CD300a is differentially expressed among B cell subsets, although its expression in immunoglobulin (Ig)M+ B cells is not well known. We identified a B cell subset expressing CD300a and high levels of IgM (IgMhiCD300a+). The results showed that IgMhiCD300a+ B cells were CD10-CD27+CD25+IgDloCD21hiCD23-CD38loCD1chi, suggesting that they are circulating marginal zone (MZ) IgM memory B cells. Regarding the immunoglobulin repertoire, IgMhiCD300a+ B cells exhibited a higher mutation rate and usage of the IgH-VDJ genes than the IgM+CD300a- counterpart. Moreover, the shorter complementarity-determining region 3 (CDR3) amino acid (AA) length from IgMhiCD300a+ B cells together with the predicted antigen experience repertoire indicates that this B cell subset has a memory phenotype. IgM memory B cells are important in T cell-independent responses. Accordingly, we demonstrate that this particular subset secretes higher amounts of IgM after stimulation with pneumococcal polysaccharides or a toll-like receptor 9 (TLR9) agonist than IgM+CD300a- cells. Finally, the frequency of IgMhiCD300a+ B cells was lower in people living with HIV-1 (PLWH) and it was inversely correlated with the years with HIV infection. Altogether, these data help to identify a memory B cell subset that contributes to T cell-independent responses to pneumococcal infections and may explain the increase in severe pneumococcal infections and the impaired responses to pneumococcal vaccination in PLWH.

Safety of Plasma Rich in Growth Factors (PRGF) as additive to healthy human sperm samples: a pilot study.

OBJECTIVE: The aim of our study was to assess if the addition of PRGF to healthy human sperm affects its motility and vitality. METHODS: This was a prospective study, with 44 sperm donors on whom sperm analysis was performed. Nine mL of blood was collected and PRGF was obtained using PRGF-Endoret® technology. The influence of different dilutions of PRGF (5%, 10%, 20%, 40%) applied to 15 sperm donors was compared, and sperm motility was assessed after 30 minutes. In the second part of the study, 29 sperm donors were studied to analyze the influence of 20% dilution of PRGF at 15, 30 and 45 minutes in fresh and thawed sperm samples. Motility was assessed after the addition of PRGF and after analysis each aliquot was frozen. After thawing, concentration and motility were assessed at the same time periods. RESULTS: There were no differences in sperm motility in fresh samples between dilutions of PRGF when assessed 30 minutes after administration, nor between them, nor when compared to the control group immediately prior to treatment. No trend was observed between motility and PRGF dilution in linear regression analysis. There were no significant differences in thawed samples. CONCLUSIONS: The administration of 20% PRGF dilution had no effect on sperm motility compared to samples without PRGF. In addition, there was no change in sperm vitality when comparing samples with and without PRGF. More studies focusing on subnormal sperm samples, analyzing different PRGF concentrations and increasing the number of study variables are needed.