Anti-CD3-stimulated T cells induce the production of multiple Ig H chain isotypes by individual human peripheral B lymphocytes.

Polyclonal activation of human B cells is achieved by coculture with T cells stimulated by mAb to the CD3 molecular complex. By formal limiting dilution analysis, approximately 60% of human peripheral blood B cells were found to produce Ig in this system. When individual B cells were cultured in microtiter wells with anti-CD3-activated T cells, more than one-third of cultures producing Ig contained multiple Ig H chain isotypes. Similar results were observed when individual IgM-expressing B cells, selected and dispersed by FACS were cultured with anti-CD3-activated T cells. The clonality of the B cells producing multiple Ig isotypes was supported by L chain analysis of the secreted Ig. Of the wells containing more than one H chain isotype, nearly 85% contained only a single L chain type. Clonality was further examined by polymerase chain reaction amplification of cDNA harvested from cultures originally seeded with individual B cells. In general, only a single VH gene family could be amplified from cultures producing more than one Ig isotype. Three separate VH regions were cloned and sequenced. One, a VHIV-mu was nearly identical to a previously described VH gene VH71.4; as second, a VHIV-gamma was very similar to a previously described VH gene segment V-79, whereas a third, a VHIII-gamma differed by 14% in nucleotide sequence from its closest germline counterpart VH3005. These results indicate that anti-CD3-activated T cells not only stimulate the majority of B cells to secrete Ig, but also induce individual B cells to produce multiple Ig H chain isotypes. Additionally, the procedure described provides a reliable method to sample a large proportion of the human peripheral B cell repertoire.