IgM+ B-cells from allergic donors partly show strong maturation by somatic hypermutations
The introduction of non-silent (mutations on amino acid level) somatic hypermutations can increase target specificity and affinity during B-cell maturation. As shown in Figure 3B, the median number of non-silent mutations was increased in VDJ heavy chain gene transcripts of class-switched B-cells and was the highest for IgA1+ and IgA2+ B-cells (IgA1: 5-11 mutations, IgA2: 10-16 mutations). The number of non-silent mutations in VDJ gene transcripts of IgM expressing B-cells, on the other hand, ranged from 0 to more than 10 in all study groups. Of note, a small number of IgM+ B-cells, mostly originating from the allergic group, consisted of highly mutated heavy chain gene transcripts with mutation numbers comparable to the other isotypes, pointing to potential maturation of 2S albumin-binding IgM+ B-cells by antigen challenge.