SEQUENCE-ANALYSIS OF REARRANGED IGV(H) GENES FROM MICRODISSECTED HUMAN PEYERS PATCH MARGINAL ZONE B-CELLS

The Peyer's patches of the terminal ileum are a source of IgA plasma c ells in the intestinal lamina propria of experimental animals. They ar e also thought to harbour IgA memory cells. However, the microanatomic al location of Peyer's patch memory cells, and whether they are also p resent in man is not known. Human Peyer's patches have a pronounced ma rginal zone (MGZ) of sIgD-negative B cells. In this study we analysed the sequence of polymerase chain reaction-amplified, rearranged IgV(H) genes from microdissected MGZ B cells, to determine whether this is a site of B-cell memory in Peyer's patches. We observed that the majori ty of Peyer's patch MGZ B cells contain heavily mutated IgV(H) genes a nd are therefore clearly memory B cells. Sequences of rearranged mutat ed genes in the MGZ have a pattern of replacement and silent mutations expected of selected products of the affinity maturation process. Rel ated clones, with identical CDR3 but different patterns of mutation, a re seen. This suggests that either these memory cells are formed as th e germinal centre selection process proceeds, or a memory cell has re- entered the germinal centre for further rounds of mutation. Interestin gly, in one patient, the MGZ in the Peyer's patches also contains a pr oportion of B cells with unmutated IgV(H) 4.21 genes.