Quantitative of anti-NP (4-hydroxy-3-nitrophenyl)-acetyl idiotype expression on spleen and thymus cells

Frequency of lambda light chain subtypes in mouse antibodies to the 2,4-dinitrophenyl (DNP) group

Of the three lambda chain subtypes made by inbred mice, chains of the lambda 1 subtype are much more frequent than those of the other subtypes (lambda 2,lambda 3) in antibodies (Ab) to those few antigenic structures that are known to elicit responses, in which lambda chains are the predominant type of light chain [(4-hydroxy-3-nitrophenyl)acetyl (NP) and dextran]. The reason for the frequency differences are not understood, and the large difference between the lambda 1 and lambda 3 frequencies is particularly puzzling, because in nearly all (about 95%) chains of these subtypes the N-terminal 97 or 98 amino acids are endoded by the same V lambda-gene segment. In an effort to identify an Ab response that has different lambda subtype frequencies, we analyzed the light chains of the Ab made by BALB/c and B6 mice in response to 2,4-dinitrophenylated chicken gamma globulin (DNP-CGG). We found that approximately 40% of the elicited anti-DNP molecules had lambda chains and of these approximately 40% were of the lambda 2 or lambda 3 subtype. Polyacrylamide gel electrophoresis indicated that the lambda 2 and lambda 3 chains were about equally abundant. Similar lambda subtype frequencies were found in the anti-DNP Ab produced by the hybridoma made with spleen cells from the same immunized mice. In the anti-DNP Ab elicited by DNP-CGG and in the anti-NP Ab elicited by NP-CGG the different lambda subtype frequencies (lambda 1/lambda 2 + lambda 3 = ca. 1.0-1.5 in anti-DNP and ca. 30 in anti-NP) were unaffected by immunizing mice with each of these antigens alone or with a mixture of the two. This finding, though preliminary, suggests that isotype-specific regulatory T cells are not responsible for the markedly different lambda subtype frequencies in anti-DNP and anti-NP Ab.

Synthesis of lambda light chain subtypes by stimulated and unstimulated mouse B cells

Inbred mouse make 3 lambda chain subtypes. The lambda 1 and lambda 3 chains have similar variable (V) regions (in both the same V gene segment [V lambda 1] is used), whereas lambda 2 and lambda 3 have similar constant (C) regions. Despite the lambda 1 and lambda 3 V region similarity, lambda 1 occurs much more frequently than lambda 3 (and lambda 2) in the serum immunoglobulins and antibody responses of most inbred strains of mice. To explore the basis for the lambda 1 predominance, we compared the rates of synthesis of the 3 subtypes and the frequencies of the B cells that synthesize them, focussing on "resting" (i.e., unstimulated) and on polyclonally stimulated B cells from spleens of unimmunized BALB/c mice. In resting cells the relative rates of synthesis and the relative frequencies of the respective B cells were in accord, indicating that the rate of lambda chain synthesis is approximately the same per resting B cell, regardless of the lambda subtype it produces. However, in the polyclonally stimulated cells, lambda 1 was made 7 times faster than lambda 2 and 10 times faster than lambda 3; normalizing these rates by the frequencies of the respective stimulated cells suggests that in stimulated B cells lambda 1 chains are made 5 times faster per cell than lambda 2 or lambda 3, while the latter are made at about the same rate per cell. In view of the marked structural homology between lambda 2 and lambda 3 genes in segments other than the V-gene segment, we suggest that the pronounced differences among polyclonally stimulated B cells in expression of the genes for the various lambda subtypes may be due to the presence of less potent enhancer-like sequences in the lambda 2 and lambda 3 genes than in the lambda 1 gene.