DIVERSITY OF IG LIGHT-CHAIN VARIABLE REGION GENE-EXPRESSION IN FETAL LAMBS

The usage of lambda and kappa light chain variable region genes in per ipheral fetal lamb B cells was assessed at intervals from 61 to 146 da ys of gestation (term = 150 days). Transcripts of 12 distinct V-lambda genes were identified, eight of which belonged to the previously desc ribed families I or II, while four segments defined a new V-lambda fam ily, provisionally called family VI. A total of six different V-kappa gene segments were identified and grouped into four families, while tw o J(kappa) gene segments were expressed. Southern blot analysis indica ted that the sheep Ig kappa locus probably contains similar to 10 V-ka ppa genes and suggests that the V gene cluster has been duplicated. Th roughout fetal ontogeny, V-kappa transcripts contained more diverse CD R3 sequences than did V-lambda transcripts, where the V-J junctions we re nearly always invariant and canonical. There was also a shift in us age of V-kappa genes and in the pattern of V-kappa-J(kappa) gene recom bination during fetal ontogeny.