Antibody elbow angles are influenced by their light chain class

We have examined the elbow angles for 365 different Fab fragments, and observe that Fabs with lambda light chains have adopted a wider range of elbow angles than their kappa chain counterparts, and that the lambda light chain Fabs are frequently found with very large (>195 degrees ) elbow angles. This apparent hyperflexibility of lambda chain Fabs may be due to an insertion in their switch region, which is one residue longer than in kappa chains, with glycine occurring most frequently at the insertion position. A new, web-based computer program that was used to calculate the Fab elbow angles is described.

Fold-specific substitution matrices for protein classification

MOTIVATION

Methods that focus on secondary structures, such as Position Specific Scoring Matrices and Hidden Markov Models, have proved useful for assigning proteins to families. However, for assigning proteins to an attribute class within a family these methods may introduce more free parameters than are needed. There are fewer members and there is less variability among sequences within a family. We describe a method for organizing proteins in a family that exhibits up to an order of magnitude reduction in the number of parameters. The basis is the log odds ratio commonly used to measure similarity. We adapt this to characterize the sequence dissimilarities that give rise to attribute differentiation. This leads to the definition of Class Attribute Substitution Matrices (CLASSUM), a dual of the BLOSUM.

RESULTS

The method was applied to classify sequences hierarchically in the lambda and kappa subgroups of the immunoglobulin superfamily. Positions conferring class were identified based on the degree of amino acid variability at a position. The CLASSUM computed for these positions classified better than 90% of test data correctly compared with 35-50% for BLOSUM-62. The expected value for a random matrix is 14%. The results suggest that family-specific data-derived substitution matrices can improve the resolution of automated methods that use generic substitution matrices for searching for and classifying proteins.

Cloning, sequence and variability analysis of expressed immunoglobulin light chain genes from yellowtail Seriola quinqueradiata

The cDNA clones encoding immunoglobulin (Ig) light (L) chain variable (V) region associated with constant (C) region were isolated from yellowtail (Seriola quinqueradiata) kidney by expressed sequence tag analysis (accession numbers: AB062619-AB062668, AB064322). The sequences of both VL and CL region contain well-conserved cysteine residues important for intra- and inter-domain interaction in mammals. Comparisons of the amino acid sequence of the CL domain with those of other species showed a high degree of similarity, with 88.3%, 59.8%, and 60.6% to those of wolf fish (Anarhichas lupus), rainbow trout IgL I isotype (Oncorhynchus mykiss) and channel catfish G isotype (Ictalurus punctatus), respectively. Multiple sequence alignments of the CL domain with those of higher vertebrates, however, did not readily allow it to be classified as kappa or lambda isotypes. Furthermore, the pI, hydrophobicity and variability of yellowtail VL regions were studied in 65 cDNA clones and the diversity was observed in CDR1, CDR2 and CDR3 regions.

Characterisation of immunoglobulin light chain cDNAs of the Atlantic salmon, Salmo salar L.; evidence for three IgL isotypes

By screening a cDNA library and analysis of DNA produced by a combined 3'RACE/5'-anchored PCR, we have isolated three isotypes of IgL in the Atlantic salmon. Two of the isotypes were homologous to rainbow trout IgL1 and L2 sequences, while the third represents a previously uncharacterised salmonid IgL. The novel type 3 CL region is homologous to spotted wolffish c1 and yellowtail sequences, while the VL region is more similar to channel catfish F class than to any other fish VL sequences. Southern analysis indicates that the gene segments of all three isotypes are organised in multiple clusters. In addition, the VL gene segments of type 3 are arranged in opposite orientation relative to the JL and CL segments, while gene segments in type 2 clusters are all in the same orientation. Although transcripts of type 1 and 3 were readily found in the spleen and head kidney, only minute amounts of type 2 transcripts were seen. The majority of type 3 messages were truncated, suggesting that spliced and full-length transcripts of this isotype probably are present at a low level compared to type 1 transcripts. The uniqueness of the type 3 VLJL sequences suggests that this isotype offers additional diversity to the antigen-binding site of Atlantic salmon immunoglobulins.

Characterization of immunoglobulin light chain isotypes in the common carp

Two or three isotypes of immunoglobulin (Ig) light (L) chain have been demonstrated in several teleost species thus far. A reverse transcription-polymerase chain reaction (RT-PCR) strategy was used with the aim of isolating cDNA clones encoding IgL chain from the common carp ( Cyprinus carpio. L.) different from the previously isolated isotype, designated L1A. cDNA clones representing two novel isotypes, designated L1B and L3, were obtained in this study. For CL segments, L1B sequences were similar to type L1/G in various teleost species, as well as L1A, while L3 sequences were closely related with type L3/F in catfish and zebrafish. For VL segments, however, L1A sequences demonstrated higher similarity to L3 rather than L1B. These results were also supported by the phylogenetic study. The similarity found between L1A and L3 VL sequences was based on the very high degree of nucleotide identity in FR1, and/or FR2 to FR3, strongly suggesting the involvement of interlocus recombination between them. Southern blot analyses suggested that the locus of L1B has a cluster-like organization, but that those of L3 and L1A are currently unknown due to cross-hybridization between those VL probes. Northern blot analyses showed that CL mRNA of each isotype was expressed in lymphoid tissues examined, particularly strongly in pronephros, and was predominantly composed of approximately 1-kb and 0.6-kb transcripts, possibly corresponding to fully spliced (LVJC) and truncated (JC/J-C) forms, respectively.

The diagnostic value of kappa/lambda ratios determined by flow cytometric analysis of biopsy specimens in B-cell lymphoma

Flow cytometry (FC) is widely utilized in the diagnosis of lymphoma and the light chain ratio (LCR) is especially useful in the diagnosis of B-cell malignancy. In this study we analysed, retrospectively, the predictive value of the LCR in the diagnosis of B-cell lymphoma in 105 consecutive patients with persistent lymph node enlargement or extranodal masses who underwent biopsy. We used a receiver-operating characteristic curve to establish a LCR threshold value of 2.0. The specificity, sensitivity, positive and negative predictive values were 92.3%, 73.1%, 90% and 77%, respectively. We concluded that determination of LCR is a useful adjunct to pathological diagnosis.

Ig light chain variability in DNP(494)-KLH immunised sea bass (Dicentrarchus labrax L.): evidence for intra-molecular induced suppression

The coding sequence of the sea bass light chain was obtained by sequential anchored PCR on a head kidney cDNA library of a DNP(494)-KLH immunised sea bass. The cDNA sequence obtained codes for a leader peptide of 21aa and a mature IgL chain of 223aa. Both the amino acid sequence comparisons and neighbour-joining trees showed that the IgL chain of sea bass obtained is of the L1/G type. To study the variability of the light chain, additional PCRs on the cDNA library and cDNA from pooled head kidneys were performed. Multiple alignment of unique sequences (N=17) could be performed without introducing gaps, and showed extremely low variability in CDR1, and no variability in CDR2 or CDR3. A possible explanation for this low variability of the IgL1 chain might be the enhanced expression of monospecific anti-DNP antibodies. The isolation and characterisation of partial genomic and cDNA IgL sequences, which showed normal variability, corroborate this explanation.

Characterization of three isotypes of immunoglobulin light chains and T-cell antigen receptor alpha in zebrafish

The zebrafish (Danio rerio) has become a significant model for understanding the developmental regulation of gene expression and holds considerable potential for characterizing the development of the immune system. Using a number of different approaches, including heterologous hybridization and short-primer PCR, cDNAs for three different classes of light-chain genes were identified and characterized. The zebrafish light chains are similar to trout type 1, trout type 2, and catfish type F, respectively. T-cell antigen receptor alpha (TCRalpha) was also identified and characterized. A high proportion of unusual transcripts including sterile transcripts, germline VJC transcripts, aberrant splice forms, and V-V transcripts were encountered in the immunoglobulin and TCR cDNAs examined. The light-chain and TCRalpha loci each consist of multiple families of V gene segments, apparent even from the small numbers of cDNAs of each isotype sequenced. The gene sequences reported provide an essential set of markers of both B- and T-cell lineages that will facilitate investigations of immune system development.

The immunoglobulin light chain in poikilothermic vertebrates

The immunoglobulin light chains are classified as kappa or lambda in mammals and birds (homeothermic vertebrates), but the traditional criteria for this classification are not applicable to the light chains found in poikilothermic vertebrates. Still it is possible to find some relationships between Ig light chain sequences in these animals and in those of the homeothermic animals. It is generally accepted that the Ig light chains contribute to the antigen binding capacity of antibodies and the variability is approximately similar in all studied vertebrate species except the elasmobranchs. This might be explained by the organisation of the Ig light chain locus in these animals and the fact that the variable and joining DNA segments are joined in the genome. These conclusions are limited by the small number of species studied in this respect.

Immunoglobulin light chain class multiplicity and alternative organizational forms in early vertebrate phylogeny

The prototypic chondrichthyan immunoglobulin (Ig) light chain type (type I) isolated from Heterodontus francisci (horned shark) has a clustered organization in which variable (V), joining (J), and constant (C) elements are in relatively close linkage (V-J-C). Using a polymerase chain reaction-based approach on a light chain peptide sequence from the holocephalan, Hydrolagus colliei (spotted ratfish), it was possible to isolate members of a second light chain gene family. A probe to this light chain (type II) detects homologs in two orders of elasmobranchs, Heterodontus, a galeomorph and Raja erinacea (little skate), a batoid, suggesting that this light chain type may be present throughout the cartilaginous fishes. In all cases, V, J, and C regions of the type II gene are arranged in closely linked clusters typical of all known Ig genes in cartilaginous fishes. All representatives of this type II gene family are joined in the germline. A third (kappa-like) light chain type from Heterodontus is described. These findings establish that a degree of light chain class complexity comparable to that of the mammals is present in the most phylogenetically distant extant jawed vertebrates and that the phenomenon of germline-joined (pre-rearranged) genes, described originally in the heavy chain genes of cartilaginous fishes, extends to light chain genes.

Preferential expression of human lambda-light-chain variable-region subgroups in multiple myeloma, AL amyloidosis, and Waldenström's macroglobulinemia

We have compared the distribution of lambda-light-chain variable-region (V lambda) subgroups among Ig lambda molecules found in the serum of normal individuals with that of monoclonal Ig lambda components obtained from patients with plasma cell and related immunoproliferative disorders. A panel of monoclonal antibodies specific for each of the major human V lambda subgroups--V lambda I, V lambda II, V lambda III, V lambda IV, V lambda VI, and V lambda VIII--was used in a highly sensitive enzyme-linked immunosorbent assay (ELISA) to quantitate each of these populations. The mean distribution of Ig lambda I, Ig lambda II, Ig lambda III, Ig lambda IV, Ig lambda VI, and Ig lambda VIII molecules in serum specimens collected from 20 normal adults was approximately 40, 3, 43, 5, 5, and 3% of the total Ig lambda population, respectively. In contrast, that of monoclonal IgG, IgA, and IgD proteins and Bence Jones proteins obtained from patients with multiple myeloma and related gammopathies (n = 196) was approximately 27, 28, 39, 5, 0, and 1%, respectively. The percentage of monoclonal Ig lambda II components found in individuals with AL lambda amyloidosis (n = 41) was comparably increased to that seen in multiple myeloma and was even higher in patients with Waldenström's macroglobulinemia (n = 16), in whom 63% of the IgM lambda proteins were of the V lambda II subgroup. Also evidenced were differences in the distribution of other V lambda subgroups in the disease states: Most striking was the predominance (41%) of the V lambda VI subgroup among monoclonal lambda chains obtained from patients with AL amyloidosis and that this subgroup was found exclusively on amyloidosis-associated proteins. No Ig lambda VI-type myeloma- or macroglobulinemia-related proteins were identified. The observed alterations in V lambda subgroup distribution among "pathologic" monoclonal Igs were attributed to the particular disease and not related to the heavy-chain class. Our finding that certain V lambda subgroups are nonstochastically expressed in lambda-type multiple myeloma, AL amyloidosis, and Waldenström's macroglobulinemia provides evidence for abnormal VL gene usage in these disorders and, thus, furnishes new insight into their pathogenesis.

Relevance of class, molecular weight and isoelectric point in predicting human light chain amyloidogenicity

The ability to predict the amyloidogenicity of certain light chains may facilitate an earlier diagnosis of AL amyloidosis and, possibly, lead to more effective treatment. Using current methods, available in clinical chemistry laboratories, we assessed the class, the relative molecular mass (Mr) and the isoelectric point of urinary monoclonal light chains from 35 patients with AL amyloidosis (A+) and 51 without amyloidosis (A-). The light chain class (LCC) was lambda in 77% and 45% of A+ and A- patients, respectively. Light chain fragments (LCF) with low Mr (12-18 x 10(3) were detected in the urine of 30/35 A+ patients and in 15/51 A- ones. The mean (SD) isoelectric point (pI) of A+ light chains was 4.8 (1.1) while in A- patients it was 6.2 (1.6). Univariate analysis showed significant differences between the two groups for the three parameters. Discriminant analysis gave a function which allowed a correct allocation of 81% of the cases between the two groups.

Human monoclonal antibodies to influenza virus: IgG subclass and light chain distribution

Three adults and three children were immunized with inactivated or live attenuated influenza vaccines and 98 IgG monoclonal antibodies derived from EBV immortalization of their blood lymphocytes were studied. All antibodies reacted specifically with influenza A H3N2 or H1N1 whole virus and 73 of 74 tested reacted with the purified HA glycoproteins. The majority (76%) of 77 monoclonal antibodies adequately tested by ELISA or solid phase RIA contained lambda light chains. ELISA analysis of the IgG subclass of the six persons' postimmunization anti-influenza serum activity and of monoclonal antibodies derived from them showed a similar predominance of IgG1.

Distribution of immunoglobulin classes in plasma cells in various kinds of synovitis

Sixty-five cases of synovitis corresponding to eight groups (seropositive and seronegative rheumatoid arthritis (RA), ankylosing spondylitis, psoriatic arthritis, post-traumatic arthritis, osteoarthritis, osteonecrosis and unclassified synovitis) were investigated in specimens stored as paraffin blocks. Immunoglobulin class content (heavy chains: G, A, M and their associated light chains: K, L) of the plasma cells was determined by the immunoperoxidase method. Plasma cells were observed in all cases in both RA groups but not in all cases of the other groups. All three classes of immunoglobulins were observed. The proportion of IgM cells was numerically larger in seropositive rheumatoid arthritis than in seronegative RA. However, due to the great case-to-case dispersion and small group size, this difference was not significant. A routine investigation of intracellular immunoglobulins cannot, therefore--at least with present knowledge--contribute to the diagnosis or prognosis of a given case of synovitis.

Immunoglobulin light chain classes in a teleost fish

Analysis of predominant, approximately 700,000 dalton serum antibody (Ab) of the channel catfish by SDS-PAGE revealed only one molecular mass species of heavy (H) chain (approximately 70,000 daltons), whereas a marked heterogeneity in the relative mobilities of the light (L) chains was evident. Three molecular mass L chain variants of approximately 26,000, approximately 24,000, and approximately 22,000 daltons were observed. The relationships between the L chain variants were not clear until mouse monoclonal Ab (mAb) reactive with catfish immunoglobulin (Ig) were developed. Two of these mAb, designated 3F12 and 1G7, were found to independently recognize different populations of catfish Ig. In addition, when these two mAb were used in combination they immunoprecipitated greater than 95% of specifically purified catfish anti-DNP or anti-fluorescein Ab. The L chains of catfish Ig recovered from immunoabsorbent affinity matrices conjugated with either mAb 3F12 or 1G7 were found to be clearly distinct. Monoclonal Ab 3F12 reacted with a subpopulation of catfish Ig that contained the approximately 24,000 and approximately 22,000 dalton L chain variants, whereas mAb 1G7 reacted with another subpopulation of catfish Ig that contained only the approximately 26,000 dalton L chain variant. Solid phase plate binding assays with the use of mildly reduced catfish Ig H and L chains showed that both of these mAb preferentially reacted with catfish L chains. Subsequent analysis of the two antigenically distinct L chain populations by peptide mapping procedures demonstrated that these L chains were structurally different. Furthermore, analysis of the serum from individual catfish showed the presence of both L chain types in each of 25 catfish examined. These studies strongly suggest that distinct L chain classes have evolved in fish.

Characterization of the subclasses and light chain types of IgG antibodies to rubella

IgG subclasses of antibodies to rubella were determined in indirect enzyme linked immunoassay (ELISA) with monoclonal antibodies specific for human IgG1, IgG2, IgG3 and IgG4. Eleven sera from women with long past history of rubella, two hyperimmune and five non-hyperimmune immunoglobulin preparations were tested. Light chain types of the antibodies were tested in ELISA with polyclonal specific antibodies to kappa and lambda chains. Antibodies to rubella in the sera as well as in the immunoglobulin preparations were found in the IgG1 subclass only. Both light chain types were present in the antibodies.

Mouse monoclonal antibodies against rabbit b6 allotype and their use for characterization of light-chain subpopulations

Mouse anti-allotypic hybridomas directed against different antigenic determinants of the b6 rabbit allotype have been raised. The fine specificity of these monoclonal antibodies (mAbs) was determined by radioimmunoassay and it was possible to classify them into three groups, each directed against distinct epitopes of the b6 allotype. Hare "b6" IgG were tested with anti-b6 mAb and no reaction was found indicating that the number of allotopes present on b6 molecules is greater than the three detected by the mAb. Comparative analysis by precipitation in gel of IgG from homozygous b6/b6 rabbits using mouse mAb and rabbit anti-b6 antibodies suggested that at least two categories of molecules can be discriminated. The observation of b6 subpopulations was confirmed by isolation of a minor subpopulation of IgG on a mouse monoclonal immunoadsorbent.

Reactive lymphoid hyperplasia with single class (monoclonal) surface immunoglobulin

Lymphoid tissues from 12 patients were diagnosed as reactive lymphoid hyperplasia, but surface immunoglobulin studies revealed monoclonal (single class) immunoglobulin staining patterns. Infectious, autoimmune, and immunodeficient conditions were diagnosed on the basis of histology and clinical features. Such surface immunoglobulin restriction has been used as an indicator of a neoplastic lymphoid proliferation, but the cases of these patients, in whom the histologic diagnosis was benign, emphasize the importance of a multiparameter approach to diagnosis. Although at the time of this report none of the patients still available to follow-up study have developed known lymphoid neoplasms, the possibility that monoclonal SIg patterns are a harbinger of neoplastic disease makes continuing follow-up of such patients important.

Isoelectric focusing of the human IgG light chains: a classification of the fractions and their normal values

The method of isoelectrofocusing was employed to obtain a reproducible pattern of human IgG light chain bands. The map of IF spectra, which contained 13 main fractions and some subfractions, was delineated. Isoelectric points of these fractions and their quantitative relations in 10 healthy individuals were determined. Initial studies performed in 3 patients with monoclonal immunoglobulins and in 1 patient with gastric ulcer, negative for monoclonal protein, showed significant deviations from normal values in certain fractions of the IF spectrum.

Production of monoclonal antibodies with haemagglutination-inhibition activity to the Skalica strain from the tick-borne encephalitis complex

Hybridomas secreting monoclonal antibodies with haemagglutination-inhibition (HI) activity to the Skalica strain of tick-borne encephalitis (TBE) complex were prepared by the fusion of P3-NS1-Ag4-1 myeloma cell line with spleen cells of BALB/c mice immunized with the purified Skalica strain. The highest titres of monoclonal antibodies obtained from the hybridomas S-9, S-15 and S-16 ranged from 512 to 10,240, respectively; the ascitic fluid contained as many as 4.6 mg/ml of monoclonal antibodies. Its analysis by Ouchterlony's double immunodiffusion, agarose electrophoresis, and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed the presence of monoclonal antibodies with mu isotype of the heavy and kappa isotype of the light chain. The specificity of the monoclonal antibodies was proved using 11 different antigens from family Togaviridae in the HI test.

Estimate of the light chain repertoire size of fetal and adult BALB/cJ and CBA/J mice

The potential light chain repertoires expressed by IgM antibodies of fetal liver and adult spleen cells were compared. B cells from these sources were stimulated by the polyclonal mitogen bacterial lipopolysaccharide and after 3 days were fused to construct hybridomas. The light chains synthesized by these hybridomas were isolated by electrophoresis and their heterogeneity was examined by isoelectric focusing. A total of 109 BALB/c and 77 CBA/J hybridoma-derived light chains obtained from fetal liver and adult spleen cells were analyzed in this way. Fifty-three and 45 unique light chains were obtained from BALB/c and C57BL/6 hybridomas, respectively. Some of these were repeated more frequently than others, but no significant differences were seen in the heterogeneity of the light chain spectrotypes of fetal and adult CBA/J and BALB/cJ mice. Furthermore, the kappa:lambda ratio of light chains were the same in fetal liver as adult-derived hybridomas. These results show that the heterogeneity of light chains as determined by IEF and the kappa:lambda ratio of IgM immunoglobulins is established very early in ontogeny.

Light-chain profiles in sera from patients with subacute sclerosing panencephalitis

Sera from 2 subacute sclerosing panencephalitis (SSPE) patients were absorbed with a concentrated preparation of measles virus. Measles-specific IgG was eluted from the precipitates containing measles antigen-antibody complex. These IgGs, when subjected to immunofixation after isoelectric focusing showed a number of oligoclonal bands with one type of light-(L) chain. In urea polyacrylamide gel electrophoresis, the reduced and alkylated measles-specific IgG showed 1-3 homogeneous L-chain bands, whereas IgG isolated from unabsorbed sera and IgG isolated from supernatants of SSPE sera after absorption with measles virus showed a diffuse L-chain band. It can be concluded that in SSPE, measles virus is responsible for the synthesis of L-chain with restricted heterogeneity.

Anti-acetylcholine receptor antibody: use of polyethylene glycol as an aid to precipitation of antibody-receptor complexes in determination of light chain and subclass

Polyethylene glycol 6000 (PEG) was used as an aid to precipitation of antibody-acetylcholine receptor (AChR) complexes. In the absence of anti-human IgG, 8% PEG can be used to precipitate antibody-AChR complexes. In the presence of low titre specific antiserum, 3% PEG selectively precipitates anti-IgG-IgG-AChR complexes and allows analysis of light chain and subclass contribution to the anti-AChR. The specificity of the various antisera is presented and results in 16 patients described.

Fish lymphocytes differ in the expression of surface immunoglobulin

Catfish peripheral blood and splenic lymphocytes were assayed for surface immunoglobulin using fifteen different mouse hybridoma antibodies to catfish immunoglobulin (Ig). These studied showed that this battery of monoclonal antibodies did not detect significant amounts of Ig on all lymphocytes. Unlike polyclonal antisera which demonstrated nearly 100% surface Ig+ cells, the monoclonal antibodies detected approximately 40% surface Ig+ cells. Furthermore, the percentage of Ig+ cells reactive with two of these monoclonals, tentatively shown to react with two different types of catfish light chains, was found to be nearly additive when the two antibodies were mixed. Thus it seems that fish lymphocytes, like their mammalian counterparts, have two different populations of lymphocytes; one which contains abundant surface Ig and one which does not. Whether these two types of cells represent the fish equivalents of B and T cells remains to be determined.

Further structural and antigenic studies of light-chain amyloid proteins

The major subunit protein of amyloid fibrils (758) isolated from a patient with systemic amyloidosis and studied by N-terminal amino acid sequence analysis was found to be almost identical to the sequence of a V lambda IV Bence-Jones protein and a previously described A lambda IV amyloid protein. The two A lambda IV amyloid proteins showed strong antigenic cross-reaction, appearing as antigenic identity in double immunodiffusion tests using anti-A lambda IV antiserum raised against one or the other of the two proteins. In addition, another new A lambda V amyloid fibril protein (R.S.) showed strong amino acid sequence homology and antigenic identity in double immunodiffusions with the prototype of the A lambda V subgroup (the AR protein). Finally, 20 primary or myeloma-associated amyloid proteins were characterized using antisera against the AA and several Ig light-chain-derived amyloid proteins.

The immunological characterization of human antibodies to factor VIII isolated by immuno-affinity chromatography

Nine human antibodies to factor VIII were isolated from haemophilic plasmas by affinity chromatography and gel filtration and six were subsequently subjected to immunological characterization. Three partially purified preparations were similarly characterized. Eight of the antibodies were characterized as being exclusively IgG and one preparation was found to contain IgM. Seven of the antibodies contained only a single light chain type, four being of type lambda and three of type kappa. Two antibody preparations contained both kappa and lambda light chains. In four of the preparations, only a single heavy chain sub-class could be demonstrated, three of IgG3 and one of IgG4. Of the remainder, three were a mixture of IgG3 and IgG4 sub-classes and one contained both IgG2 and IgG4. IgG sub-classification could not be achieved with the IgM-containing preparation. These results demonstrate a restricted heterogeneity of light and heavy chains in human antibodies to factor VIII.

Immunoglobulin evolution: chemical study of clawed toad (Xenopus laevis) heavy and light chains

NH2 terminal amino acid sequence determinations of clawed toad (Xenopus laevis) immunoglobulins indicate that approximately 30% of the heavy chains and less than 5% of the light chains have unblocked NH2 termini. The major amino acid sequence of the X. laevis 7S immunoglobulin heavy chains is the same as that of the 19S immunoglobulin heavy chains. Thus in the synthesis of the heavy chains, the VH genes coding for unblocked heavy chains can associate with CH genes of both the 19S and 7S classes. This association is particularly important in amphibians because, in contrast to mammals and birds, the majority of amphibian antibody-producing cells synthesize both 19S and 7S immunoglobulins and do not participate in the 'genetic switch' characteristic of lymphocyte differentiation in higher organisms. In X. laevis, the major amino acid sequence at the first twenty-four positions of the unblocked heavy chains shows approximately 54% difference from the prototype amino acid sequence of the mammalian VHIII subgroup. Thus, the VHIII gene(s) must have started to appear after the evolutionary divergence of the common ancestor of mammals and birds from the amphibian line. The amino acid composition of the X. Laevis 7S immunoglobulin heavy chains differs from that of its 19S immunoglobulins as well as those of human IgG and IgA. These data support the concepts (a) that amphibian 7S and 19S immunoglobins belong to distinct classes and (b) that amphibian 7S immunoglobulin does not resemble mammalian IgG or IgA.

[Certain characteristics of isolation of human myelomic IgG of different subclasses and their distribution according to the allotypes, subclasses and types of light chain]

A combination of the methods of preparative electrophoresis in agar gel and of the ion-exchange chromatography on DE-32 cellulose permitted to obtain 32 immunochemically pure human myelomic IgG. The proteins of the first three subclasses were obtained by elution in the 0.01 phosphate buffer at pH 7.6. IgG4 was eluted with the increase of the gradient to 1 M NaCl in the phosphate buffer. Of the 32 human myelomic IgG 26 represented IgG1,4--IgG2, 1--IgG3, and 1--IgG4. Among the 26 IgG1 11 were of the Gm(a) allotype, and 15 proteins had the Gm(f) determinant; one IgG2 protein was Gm(n+) and 3--Gm(n-). One IgG3 protein was referred to the Gm(b) variant. The majority of the IgG proteins of the subclass I had chi-type of the L-chains, and the chi: lambda ratio constituted 2.71.