Allergic and tolerant donors possess more class-switched 2S
albumin-binding B-cells than non-atopic controls
All successfully sequenced heavy chain gene transcripts were initially
analyzed for isotype distribution, as class-switching is mostly
accompanied by somatic hypermutation maturation upon antigen challenge.
Overall, IgM was the most dominant isotype across all groups. Notably,
its prevalence was much lower in allergic (47%) and tolerant (53%)
donors than in the non-atopic reference group (94%), indicating more
antigen-challenged and matured specific B-cells originated from allergic
and tolerant patients. Moreover, the prevalence of IgA2-expressing
B-cells was increased in the tolerant group (20%), while a comparable
distribution was observed in allergic and non-atopic donors (2%), as
shown in Figure 3A. This finding suggests potential protection by
specific IgA in tolerant patients, as IgA is generally able to prevent
mucosal antigen crossing22. Regarding IgE, only a
small number of V(D)J gene transcripts derived from IgE+ B-cells were
successfully amplified (allergic: 1; tolerant: 2), possibly due to the
extreme low abundance (0.002-1%) of IgE+ B-cells within the
circulation23. Even though slightly higher proportions
are known for IgG3+ (~1%) and IgG4+ B-cells
(~0.75%)24, 25, no V(D)J gene
transcripts derived from IgG3+ and IgG4+ B-cells were amplified.
Overall, the individual isotype distribution varied for each patient,
e.g. 2S albumin-binding B-cells of the allergic patient 4 were
predominantly IgM+ B-cells, while those of patient 1 were predominantly
IgG+ B-cells with a shift to class-switched B-cells in peanut allergic
and tolerant patients. This indicates that the 2S albumin-binding
B-cells from allergic and tolerant patients were more often matured and
antigen-challenged B-cells compared with the non-atopic control group.