A higher serum IgA is related to lower levels of bacterial DNA in blood. These subjects have more IgA+ switched B cells, and fewer inflammatory complications. (A) Serum IgA and bacterial 16 ribosomal DNA (rDNA). Serum IgA is inversely related to the content of bacterial 16S ribosomal DNA (rDNA) in 111 paired samples (Spearman r, two tailed test P = 0.006; r = −0.3224). Subjects in Group 1 (no inflammatory complications) are distinguished from those with these complications (Group 2). (B) IgA+ SM B cells. The numbers of IgA+ SM B cells for 89 subjects were closely correlated with the numbers of total isotype SM B cells (Spearman r, two tailed test P = 0.002; r = −0.3265). Subjects in Group 1 (no inflammatory complications) are distinguished from those with these complications (Group 2). (C) IgA+ SM B cells and serum IgA. The numbers of IgA⁺ SM B cells are related to the baseline level of serum IgA of the same 92 patients (Spearman r, two tailed test P = 0.002; r = −0.322). Subjects in Group 1 (no inflammatory complications) are distinguished from those with these complications (Group 2). (D) IgA+ SM B cells and 16S ribosomal DNA (rDNA). The number of IgA⁺ SM B cells was also inversely related to the bacterial ribosomal DNA (rDNA) levels in the same 93 serum (Spearman r, P = 0.007; r = −0.2808). Again, CVID subjects in groups 1 and 2 are indicated.