Mouse Kappa Light Chain Research Articles

Nucleotide sequence of a mouse kappa light chain cDNA cloned in a bacterial plasmid

A mouse MOPC21 cDNA previously cloned in plasmid pMB9(Higuchi et al. , Proc. Natl. Acad. Sci. 73 (1976) 2136–2140; Wall et al. , Nucleic Acid Res. 5 (1978) 3113–3128) and is designated pL21-3 has been extensively characterized. Cleavage of pL21-3 with Hpall has shown the insert to be 910 basepairs long, consistent with the length of the entire variable and constant regions and the untranslated regions. Digestion of pL21-3 with various restriction endonucleases has established that the insert sequence starts from parts of the 5′ leader region and extends downstream to include the untranslated 3′ terminus. 131 nucleotides in the variable region corresponding to amino acids 49–91 have been determined.

Chromosomal assignment of the mouse kappa light chain genes.

Mouse-hamster somatic cell hybrids containing a variable number of mouse chromosomes have been used in experiments to determine which mouse chromosome carries the immunoglobulin kappa light chain genes. It has been shown by nucleic acid hybridization that the kappa constant gene and the genes for at least one variable region subgroup are on mouse chromosome 6. This somatic cell genetic mapping procedure appears to be general and can be applied to any expressed or silent gene for which an appropriate nucleic acid probe exists.

Multiple related immunoglobulin variable-region genes identified by cloning and sequence analysis.

We have identified at least six EcoRI fragments of mouse DNA that encode variable-region gene sequences closely related to the mouse kappa light chain, MOPC-149. Two of these fragments have been cloned, and the entire nucleotide sequence of the variable-region genes encoded on each has been determined. Both genes encode closely related variable-region sequences extending from codon position 1 through position 97. Neither fragment encodes a constant-region sequence. Although both genes are closely related, they differ from one another and from the sequence expressed in the MOPC-149 cell from which they were cloned. These few differences cluster within the complementarity-determining regions although several occur in framework sequences as well. We therefore conclude that an antibody-producing cell contains genetic information corresponding to its expressed sequence and several other closely related but silent sequences. These initial results raise the possibility that similar sets of genes might exist corresponding to each of the many subgroups already identified among mouse kappa light chains. If true, this would further suggest that the mouse genome might be rich enough in variable-region genes so as to encode a major portion of the variable-region repertoire.

Partial amino acid sequence of the precursor of immunoglobulin light chain programmed by messenger RNA in vitro.

The five proteins programmed in a cell-free system by a mouse kappa light chain messenger RNA were labeled with [3H]leucine and subjected to amino acid sequence analyses. In all five proteins, 20 amino acid residues precede the amino terminus of the mature protein, indicating that there is one major point for the initiation of messenger RNA translation. The abundance (30 percent) of leucine residues in the extra piece (leucine at positions 6, 7, 8, 11, 12, and 13) indicates that this moiety is hydrophobic. Furthermore, it seems that the precursor may have an additional extra piece at the carboxyl terminus.

IMMUNOGLOBULINS ON THE SURFACE OF THYMUS-DERIVED CELLS ENGAGED IN THE INITIATION OF A HUMORAL IMMUNE RESPONSE

Preculture treatment of normal spleen cells with antiserum against mouse kappa light chains and complement was found to inhibit in vitro responses of these cells to TNP and erythrocyte (carrier) antigens, primarily by elimination of a thymus-derived helper component required for the response. Spleen populations inactivated in this way could be reconstituted with irradiated, carrier-immune spleen cells or with carrier-educated thymus-derived spleen cells. The ability of helper populations (i.e. irradiated, carrier-immune spleen cells or carrier-educated thymus-derived spleen cells) to enhance the response of normal spleen cells to hapten was eliminated by pretreatment of the helper cells with anti-kappa serum and complement. No significant effect of anti-kappa and complement treatment on precursor cell populations in normal spleen or bone-marrow-derived spleen could be demonstrated. The data are interpreted as evidence for the presence of immunoglobulin components. The function of these molecules is not established but it would be reasonable to assume that they are involved in antigen recognition, on the surface of thymus-derived cells.