Figure 4.

Paired-chain plasmablast repertoire sequence characteristics are similar to those observed in bulk B cell heavy-chain sequencing. Blood plasmablasts were single-cell sorted and tagged with cell-specific barcode oligonucleotides to enable sequencing of their paired heavy- and light-chain genes, yielding a mean of 436 full-length variable region paired sequences per subject. Plasmablasts were defined as CD19^int/+CD3⁻CD33⁻CD14⁻CD20^int/−CD27⁺CD38^hi live single cells. (A) Degree of clonal lineage expansion was significantly increased in plasmablasts from untreated Lyme disease. Percent clonality was calculated, across serial time points, as the percent of cells that were part of an expanded clonal family out of the total number of paired sequences from that time point. (B) Clonality showed a trend of increase in plasmablasts from patients with disseminated erythema migrans rash. (C) As was seen with bulk B cells, patients with a shorter duration of symptoms (return to health) exhibited significantly greater plasmablast clonality than those with persistent symptoms. (D) Mutations from germline and (E) CDR3 amino acid lengths showed minor variations among patient subsets. P values are ANOVA with Dunnett’s (A) or Sidak’s (B–E) multiple comparisons tests. Dashed lines represent the median value of healthy controls, and error bars represent SE.