Immunologic memory to phosphocholine. V. Hybridomas representative of group II antibodies utilize V(k)1-3 gene(s)

The anti-phosphocholine (PC) memory response of BALB/c mice to PC-KLH contains two groups of antibodies distinguished by fine specificity and by expression of the T15 idiotype that dominates Group I but not Group II anti-PC antibodies. The contribution of V(k) genes to this diversity was investigated by the analysis of L chains from PC-binding hybridoma proteins (PCBHP) representative of Group I and Group II. N-terminal amino acid sequence analysis was performed on the L chains of three independently derived Group II PCBHP up to residue 23 (PCG1-1) or 21 (aPC-111-1 and aPC-12-3). These three sequences differed from each other by only one or two residues, but differed by approximately 50% from the L chains of the Group I-like PC-binding myeloma proteins (PCBMP); the Group II sequences are closely related to V(k)1-3. Isoelectric focusing analysis was also performed on the L chain of PCG1-1, as well as on L chains from PCBHP typical of Group I antibodies, and from an atypical PCBHP differing from Groups I and II in fine specificity. A Group I PCBHP and the atypical PCBHP expressed L chains related to V(k)8 and V(k)24, respectively. The L chains of another Group I PCBHP and of the Group II protein, PCG1-1, appeared different from those found in the PCBMP and from each other. The results indicate a more diverse expression of L chains in the memory anti-PC response than is represented by the PCBMP; both V(k)8- and V(k)24-derived L chains (and, presumably, somatic variants), as well as products of additional V(k) genes (V(k)1-3), appear to be present in the anti-PC memory pool.