FIG. 5.

Frequency distribution for unique Vβ13a-CDR3 sequences. To assess the likelihood that Vβ13⁺ TCRs present in prediabetic islets might be involved in the recognition of a specific antigen or antigens, the number of times that a specific CDR3 sequence was present in a Vβ13 transcript was quantified as described in research design and methods. The total number of transcripts analyzed for each tissue is given in parentheses. Relatively few Vβ13a-CDR3 sequences were found only once in the pools of mRNA transcripts obtained from islets of poly I:C–treated rats (21 of 157); more were found two to four times (39 of 157) and nearly two-thirds were found more than four times (97of 157). In contrast, relatively more Vβ13a-CDR3 sequences were found only once in the mRNA transcripts from spleens of poly I:C–treated rats (28 of 106); a few more were found two to four times (33 of 106) and fewer than one-half were found more than four times (45 of 106). Among Vβ13a-CDR3 transcripts obtained from spleen cells of untreated rats, 32 of 76 were observed only once, 28 of 76 two to four times, and 16 of 76 more than four times (overall χ² = 39.5; df = 4; P < 0.0001). SPC, spleen cells.