Nonidiotypic VH antigens can be detected on human lymphocytes

Rabbit antisera to the variable region domains of an anti-alpha(1----6) dextran using E. coli-produced VL and VH fusion proteins as immunogens

Bacteria were engineered for the expression of mouse immunoglobulin light chain variable region (VL) and heavy chain variable region (VH) fusion proteins. cDNAs encoding the VL and VH of anti-alpha(1----6)dextran hybridoma protein 19.22.1 were inserted into the pATH 10 prokaryotic expression vector downstream of trp operon sequences. V domains joined to approximately 330 amino acids of the trp E gene product encoded by the expression plasmids accumulated at high levels in E. coli. In addition, the VL domain was expressed with a 15 amino acid extension at low levels in lon mutant bacteria. The trp E-VL and trp E-VH proteins were used to raise antisera in rabbits and the V specificity of the sera demonstrated.

Monoclonal anti-VH antibodies recognize a common VH determinant expressed on immunoglobulin heavy chains from various species

Our previous work using rabbit antibodies to the variable region of MOPC315 myeloma heavy chain (VH) has indicated the existence of framework determinant(s) common to many murine heavy chains. Here we report the characterization of anti-VH monoclonal antibodies (mAb) prepared in an attempt to elucidate the nature of the common VH determinant. We immunized AKR/J mice with a purified VH315 fragment and generated somatic cell hybrids by the fusion of the immune AKR/J splenocytes with the NS1 myeloma cells. Thirty-seven common anti-VH and 57 subgroup VHI-specific hybridomas have been established and characterized. Whereas the anti-subgroup mAb seemed to react with a determinant unique to the MOPC315 (mouse VHI) subgroup, all the anti-VH mAb reacted with myeloma heavy chains of different VH subgroups, class and allotypes. Antibody competition studies revealed that the VH subgroup determinants are distinct from the common VH determinants and that both were also recognized by the rabbit polyclonal antibodies. The common VH determinants were found to be "hidden" determinants on intact immunoglobulin molecules being exposed only on isolated heavy chains. Furthermore, they are sequential determinants since they are preserved on fully denatured heavy chains. The common VH determinants are shared by immunoglobulins of a wide range of vertebrates from amphibia to man and thus represent antigenic structures which were highly conserved throughout evolution.

Antigenic and structural characteristics of an immunoglobulin-related peptide purified from marmoset T-lymphoma cells

A 7800 Mr peptide, apparently derived from a 70,000 Mr immunoglobulin-related protein synthesized by a marmoset T-lymphoma cell line, bears immunoglobulin-related determinants apparently contained in a disulfide-bonded loop comparable to that of the VH fragment of classical H chain. A membrane-enriched, crude particulate fraction was prepared from marmoset T-lymphoma cells, and peptides generated by papain digestion of the particulate fraction were selectively purified by affinity chromatography using IgG purified from serum of a goat immunized with the Fab fragment of a human Waldenstrom macroglobulin. The smallest of the affinity-purified peptides was particularly reactive with unfractionated goat anti Fab (G alpha Fab) serum, purified IgG from G alpha Fab serum, and with antibodies affinity purified from G alpha Fab serum using Waldenstrom macroglobulins. Partial specificity of G alpha Fab antibodies was determined by competition radioimmunoassay and radioimmunoprecipitation assays. High-performance reverse-phase liquid chromatography was used for final purification of the smallest peptide which retained its reactivity with G alpha Fab serum and affinity-purified G alpha Fab antibodies. The apparent molecular weight of the peptide, determined by gel filtration in 6 M guanidine, was estimated at 3900 in its native state but increased to 7800 after reduction and alkylation, indicating a role for a disulfide bond in the tertiary structure of the peptide. The amino acid composition of the peptide was presented, and its possible relationship to immunoglobulin-like T-cell surface proteins was discussed.

Immunoglobulin VH determinants defined by monoclonal antibodies

Hybridoma clones secreting antibodies against common VH determinants were readily produced by fusion of cells from mice immunized with isolated V mu fragments of human immunoglobulins (Ig), but not with intact Ig molecules or isolated heavy chains. Four monoclonal antibodies to the V mu fragments of different IgM paraproteins were selected for analysis: MH-44 (mu kappa), GB-24 (mu kappa), NF-11 (gamma 1 kappa), and SA-44 (gamma 1 kappa). Each antibody reacted with the homologous V mu fragment, homologous mu chain, and normal gamma chains, but not with the intact IgM molecules, intact IgG, or isolated light chains, as determined by radioimmunoassay. The VH reaction spectra with a panel of myeloma heavy chains showed overlapping but distinctive patterns for the four antibodies. Each of the four monoclonal anti-VH antibodies appeared to react with a different "hidden" VH determinant that is not exposed on undenatured, intact Ig molecules and differs from conventional VH subgroup determinants. In immunofluorescence studies, the monoclonal anti-VH antibodies did not bind to surface Ig on viable B lymphocytes, but visibly stained subpopulations of fixed B lymphocytes, pre-B cells, and normal plasma cells. The mean frequencies of VH+ plasma cells were 30% (MH-44), 17% (GB-24), 13% (NF-11), and 3% (SA-44), and similar frequencies were obtained for the VH+ B cell subpopulations. While subpopulations of B cells could be identified at all stages in differentiation by immunofluorescence with the anti-VH antibodies, neither resting nor activated T cells expressed these VH determinants in detectable amounts.