A Homologue of the Rabbit κ-Chain Allotype b9 on IgG from a Cottontail Rabbit Free

Eight out of 12 anti-b9 antisera tested strongly bound ¹²⁵IgG of only one of four individual cottontail rabbits (Sylvilagus floridanus). In addition to this apparent polymorphism of a b9 homologue in cottontail rabbits, a polymorphism defined by some anti-b5 antisera was found. Three of 15 anti-b5 antisera reacted with IgG from only two of the four cottontail rabbits. Reactions with anti-b4 and anti-b6 were similar to those with hare IgG. Most anti-b4 and anti-b6 antisera bound the IgG from each animal. The cottontails we tested also resembled the hare with respect to their weak reactivity with some anti-a2 antisera (V_H allotype) and strong reactivity with anti-15 (an allotype localized in the Fc portion of rabbit γ-chains).