B Lymphocyte Subsets and Their Functional Activity in the Early Months of Life

In the present study we evaluated B-cell subsets and their functional development in 74 newborns from birth to 6 months of life. Moreover, we evaluated “natural antibody” production in vitro. The results documented a predominance of naiveB-lymphocytes at all time-points evaluated, decreasing from birth to 6 months (p=0.009). The percentages of CD27+IgD+and CD27+IgDnegmemory B-cells were very low at birth and significantly increased only at 6 months (p=0.02 and p<0.001, respectively). We found a significant increase only in in vitrostimulated IgG production at 6 months as compared to birth (p<0.001). Moreover, a lower secretion of anti-Pn IgM antibodies up to 6 months of age, as compared to controls was observed. Our results underline that the susceptibility and severe course of infection in the neonate can be attributed, at least in part, to the lack of pre-existing immunological memory and competent adaptive immunity.