Hinge length contributes to the phagocytic activity of HIV-specific IgG1 and IgG3 antibodies

Antibody functions such as neutralization require recognition of antigen by the Fab region, while effector functions are additionally mediated by interactions of the Fc region with soluble factors and cellular receptors. The efficacy of individual antibodies varies based on Fab domain characteristics, such as affinity for antigen and epitope-specificity, and on Fc domain characteristics that include isotype, subclass, and glycosylation profile. Here, a series of HIV-specific antibody subclass and hinge variants were constructed and tested to define those properties associated with differential effector function. In the context of the broadly neutralizing CD4 binding site-specific antibody VRC01 and the variable loop (V3) binding antibody 447-52D, hinge truncation and extension had a considerable impact on the magnitude of phagocytic activity of both IgG1 and IgG3 subclasses. The improvement in phagocytic potency of antibodies with extended hinges could not be attributed to changes in either intrinsic antigen or antibody receptor affinity. This effect was specific to phagocytosis and was generalizable to different phagocytes, at different effector cell to target ratios, for target particles of different size and composition, and occurred across a range of antibody concentrations. Antibody dependent cellular cytotoxicity and neutralization were generally independent of hinge length, and complement deposition displayed variable local optima. In vivo stability testing showed that IgG molecules with altered hinges can exhibit similar biodistribution and pharmacokinetic profiles as IgG1. Overall, these results suggest that when high phagocytic activity is desirable, therapeutic antibodies may benefit from being formatted as human IgG3 or engineered IgG1 forms with elongated hinges.

Identification of allelic polymorphism in the caprine IGHA gene

Variation in the immunoglobulin heavy alpha chain (IGHA) constant region has been reported in a number of species. In this study, the IGHA gene was investigated in goats using PCR-single-strand conformational polymorphism (SSCP) analysis and DNA sequencing. Three novel sequences were identified from 111 Boer and Angora goats. Either one or two sequences were detected in individual goats, and all the sequences shared high homology to the published ovine and bovine IGHA sequences. These sequences were predicted to encode three amino acid sequences, two with a longer hinge region and one with a shorter hinge region. The variation reported here may affect the structure of the hinge and hence the function of IgA.

Discovery of a new class of immunoglobulin heavy chain from fugu

In teleosts, the genomic organization of the immunoglobulin (Ig) heavy (H)-chain locus was thought to follow a typical translocon-type multigene structure; however, recent studies have indicated a variation in the structure and this might be teleost specific. Isotypes of the Ig H-chain, namely IgM, IgD, IgZ and IgT, have been identified. In this study, we report the discovery of a new class of IgH from fugu. This isotype was first identified from the genomic sequence of the fugu IgH locus. This novel IgH gene is composed of two constant (C) domains, a hinge region, and two exons encoding membrane regions. Surprisingly, the new IgH gene is present between the variable (V)H and Cmu regions of the locus. The C domains of the new isotype do not show any significant similarity to mammalian or fish IgH genes. The cloned cDNA from the new isotype has typical Ig H-chain characteristics and is expressed as both secretory and membrane form. Transcript analyses suggest that the new IgH from fugu might only use the joining (J)H segments present in front of the new CH domains and that the usage of DH and JH segments is specific to the isotype expressed. The expression pattern of the gene has been confirmed by in situ hybridization and PCR studies.

Characterisation of salmon and trout CD8alpha and CD8beta

The genes and corresponding cDNAs of both alpha and beta chains of the Atlantic salmon (Salmo salar) CD8 molecule have been sequenced and characterized. In addition, the cDNAs for alpha and beta chains of brown trout (Salmo trutta) and for the beta chain in rainbow trout (Oncorhynchus mykiss) have been sequenced. The cDNAs code for signal sequences which are preceded by short 5' UTRs. These are followed by typical immunoglobulin superfamily variable sequences all of which contain two conserved cysteines for the intra-chain disulphide bond. The hinge regions display conserved cysteines for dimerisation and several O-glycosylation motifs for each predicted protein. The domain sharing the highest sequence identity with mammals is the single pass transmembrane domain for all sequences. In salmon, each domain is predominantly coded for by a single exon except the cytoplasmic/3' UTR domains, which are coded for by 3 and 2 exons for the alpha and beta genes, respectively. In the alpha gene, the second cytoplasmic exon may be spliced out to form an alternative shorter transcript which if expressed would exhibit a truncated cytoplasmic tail. A splice variant found for the salmon beta gene introduces a stop codon after only 40 amino acids. Overall amino acid identities between salmonid sequences were higher than 90%, whereas they shared only 15-20% identity with species such as, chicken and human. Analysis of the expression patterns of the two salmon genes using quantitative RT-PCR shows a very high expression in the thymus. This is mirrored by the expression of the TCRalpha gene, which is known to be co-expressed with CD8 on mammalian T cells. This is the first report of a sequence for CD8beta in a teleost and together with the CD8alpha sequence, it encodes the ortholog of the CD8 co-receptor molecule on mammalian T cells.

The porcine Ig delta gene: unique chimeric splicing of the first constant region domain in its heavy chain transcripts

The pig delta gene is located approximately 3.4 kb downstream of the second transmembrane exon of the micro gene and shows a similar genomic structure to its counterpart in cow with three exons encoding the CH1, CH2, and CH3 domains. The porcine genomic deltaCH1 exon has been replaced by a recent duplication of the micro CH1 and its flanking sequences, a genetic event that also led to the formation of a short switch delta region, immediately upstream of the delta gene. The deltaCH1 exhibits a 98.7% similarity (314 of 318 bp) to the micro CH1 at the DNA level, whereas the homologies between the deltaCH2 and micro CH3, and the deltaCH3 and micro CH4 are only 33.3 and 35.8%, respectively. Either of the two CH1 exons ( micro and delta) could be observed in the expressed porcine IgD H chain cDNA sequences VDJ- micro CH1-H-deltaCH2-deltaCH3 or VDJ-deltaCH1-H-deltaCH2-deltaCH3, showing a pattern that has not been observed previously in vertebrates. In addition, transfection of a human B cell line, using artificial constructs resembling the porcine C micro -Cdelta locus, also generated both VDJ- micro CH1-deltaCH1-H1-deltaCH2 and VDJ -deltaCH1-H1-deltaCH2 transcripts. An examination of the pig delta genomic sequence shows a putative, second hinge region-encoding exon. Due to the lack of a normal branchpoint sequence for RNA splicing, this exon is not present in the normal pig delta cDNA. However, the exon could be spliced into most of the expressed transcripts in vitro in cell transfection experiments after introduction of a single T nucleotide to restore the branchpoint sequence upstream of the putative H2 exon.

Baboon immunoglobulin constant region heavy chains: identification of four IGHG genes

The increasing use of nonhuman primate models in biomedical research and especially in vaccine development requires the characterization of their immunoglobulin genes and corresponding products. Therefore, we sequenced, cloned and characterized the four immunoglobulin gamma chain constant region genes ( IGHG) present in baboons. These four genes were designated IGHG1, IGHG2, IGHG3 and IGHG4 on the basis of sequence similarities with the four human genes encoding the IgG1, IgG2, IgG3 and IgG4 subclasses and the three known rhesus macaque IGHG genes. Specifically, the baboon IgG1, IgG2, IgG3 and IgG4 sequences exhibit 90.3%, 88.3%, 86.7% and 89.6% amino acid identity to their human counterpart. The percent of amino acid identity of baboon IgG1, IgG2 and IgG3 to the corresponding rhesus macaque sequences is 98.5, 93.1 and 94.4, respectively. Therefore, baboon and rhesus macaque IGHG genes are highly homologous to each other. The majority of differences existing between baboon and human sequences are clustered in the hinge region, with the upper hinge being the most diverse and containing several proline residues. Similar to rhesus macaques, the hinge regions of all baboon IGHG genes consist of a single exon, whereas in humans the IgG3 molecule is encoded by multiple exons. These results confirm the evolutionary instability of the hinge region and indicate that functional properties associated with the hinge regions of baboon and human IgG molecules might differ between the two species.

Adaptive evolution of the IgA hinge region in primates

IgA is a major component that prevents the penetration of pathogenic bacteria into mucosal surfaces. The IgA antibody is cleaved at the IgA hinge region with high specificity by IgA-specific proteases produced by several pathogenic bacteria. We conducted a genomic sequence analysis of the IgA genes of a wide spectrum of primates, including the first intron and second exon, which consist of the hinge region and the CH2 domain, to find evidence of positive selection. Because the hinge region is quite small, we combined the largest collection of sequences that could be clearly aligned and evaluated the total numbers of synonymous and nonsynonymous substitutions on the phylogenetic tree. The nonsynonymous to synonymous substitution ratio (d(N)/d(S) test) showed that hominoids, Old World monkeys, and New World monkeys have d(N)/d(S) ratios of 5.4, 6.3, and 4.2, respectively. Fisher's exact probability tests showed statistical significance for the Old World monkey. Because the substitution rates of the flanking sequences are more or less similar to the synonymous rates of the hinge region, these high values of d(N)/d(S) should be the result of positive selection at the hinge region. Combining the high sequence variability in each population and the highly accelerated nonsynonymous substitution rates in the hinge region, we conclude that this unusual IgA evolution is a molecular evidence of adaptive evolution possibly caused by the host-parasite relationship.

The first constant-domain (CH1) exon of human IGHG2 is polymorphic and in strong linkage disequilibrium with the CH2 exon polymorphism encoding the G2m(n+) allotype in Caucasians

Here we describe a hitherto unknown proline/threonine polymorphism at residue 72 of the human IgG2 CH1 domain (EU numbering 189) and show that it is linked to the known valine/methionine polymorphism at residue 52 of CH2 (EU numbering 282) defining the G2m(n+)/G2m(n-) allotypes. We sequenced the entire constant region of the heavy-chain gene for secreted IgG2 in five IGHG2*02 homozygous individuals covering CH1, hinge, CH2, and CH3 regions (approximately 2 kb). Proline 72 in CH1 of G2m(n-) is changed to threonine in the G2m(n+) [G2m(23)] allotype. Based on the crystal structure of human IgG1, this amino acid position is expected to be surface exposed in IgG2. Besides this structural difference, we identified two silent nucleotide polymorphisms in the CH1 region and seven in the introns. Finally, we developed a sequence-specific PCR typing system detecting the polymorphisms in the CH1 and CH2 regions. We typed 64 Danish Caucasians and found that the CH1 and CH2 region polymorphisms are in complete linkage disequilibrium in this population.

Description of an ectothermic TCR coreceptor, CD8 alpha, in rainbow trout

We have cloned the first CD8 alpha gene from an ectothermic source using a degenerate primer for Ig superfamily V domains. Similar to homologues in higher vertebrates, the rainbow trout CD8 alpha gene encodes a 204-aa mature protein composed of two extracellular domains including an Ig superfamily V domain and hinge region. Differing from mammalian CD8 alpha V domains, lower vertebrate (trout and chicken) sequences do not contain the extra cysteine residue (C strand) involved in the abnormal intrachain disulfide bridging within the CD8 alpha V domain of mice and rats. The trout membrane proximal hinge region contains the two essential cysteine residues involved in CD8 dimerization (alpha alpha or alpha beta) and threonine, serine, and proline residues which may be involved in multiple O-linked glycosylation events. Although the transmembrane region is well conserved in all CD8 alpha sequences analyzed to date, the putative trout cytoplasmic region differs and, in fact, lacks the consensus p56lck motif common to other CD8 alpha sequences. We then determined that the trout CD8 alpha genomic structure is similar to that of humans (six exons) but differs from that of mice (five exons). Additionally, Northern blotting and RT-PCR demonstrate that trout CD8 alpha is expressed at high levels within the thymus and at weaker levels in the spleen, kidney, intestine, and peripheral blood leukocytes. Finally, we show that trout CD8 alpha can be expressed on the surface of cells via transfection. Together, our results demonstrate that the basic structure and expression of CD8 alpha has been maintained for more than 400 million years of evolution.

Loss of splice consensus signal is responsible for the removal of the entire C(H)1 domain of the functional camel IGG2A heavy-chain antibodies

The molecular basis for the absence of the C(H)1 domain in naturally occurring heavy-chain antibodies of the camelids was assessed by determining the entire Camelus dromedarius gamma2a heavy-chain constant gene. The organization of the camel gamma2a constant heavy-chain gene obtained from a liver genomic library appears to be typical of all other mammalian gamma genes sequenced to date. It contains the switch, CH1, hinge, CH2, CH3, M1 and M2 exons. In contrast to the case in mouse and human heavy chain diseases, the camel gamma2a gene shows no major structural defect, and its equivalent CHI exon is intact. However, sequence analysis has revealed that the splicing site, immediately after the CH1 exon, is defective due to point mutations, especially the G(+1) to A(+1) transversion seems to be detrimental. It is concluded that the loss of the splice consensus signal is responsible for the removal of the entire CH1 domain in camel gamma2a heavy-chain immunoglobulins. Additionally, a closer analysis of the hinge exon suggests the possible involvement of transposons in the genetic variation of mammalian Cgamma hinges.

The IGHG3 gene shows a structural polymorphism characterized by different hinge lengths: sequence of a new 2-exon hinge gene

Four of the five human IGHG genes (G1, GP, G2, and G4) display a hinge region consisting of a unique exon. In contrast, IGHG3 exhibits a different structure in which the hinge is constituted by four or, less frequently, three exons. We report here the nucleotide sequence of a new 2-exon hinge G3 gene found in a Mandenka individual from Eastern Senegal. A comparison of this sequence with that of 4-exon and 3-exon hinge G3 genes suggests that the 3-exon and 2-exon hinge forms arose independently by deletion events in a 4-exon hinge gene.

Sequence of ovine Ig gamma 2 constant region heavy chain cDNA and molecular modelling of ruminant IgG isotypes

Ovine mesenteric lymph node mRNA was used for PCR amplification of DNA coding for immunoglobulin gamma 1 and gamma 2 heavy chain constant regions. Primers complementary to regions of CH1 conserved between ruminants were used for upstream priming, with downstream priming on the poly-A segment. PCR products of the appropriate length were cloned and gamma positive clones selected with a CH1 conserved-region probe. Of these, gamma 1 clones were positively selected and gamma 2 clones negatively selected with a gamma 1 hinge-specific probe. Ovine gamma 2 cDNA has 93% identity of nucleotides with ovine gamma 1. Both ovine gamma 1 and gamma 2 CH1 domains encoded two consecutive cysteine residues (Cys-127, -128, Kabat numbering), an arrangement which is deduced to form a pair of disulphide bridges, one to the L chain and one as an intra-chain bridge to the uppermost Cys of the hinge, as in rabbit and goat IgG. The majority of the differences between the isotypes occur in the hinge region and an evolutionary pattern for ruminant IgG hinges can now be identified. IgG1 isotypes are typical, with hinges containing the C-terminal Cys-Pro motif, but deletion and replacement of nucleotides (in the ancestral gene) of ruminant gamma 2 has shortened the IgG2 hinge, removing the Cys-Pro motif and the consensus high affinity Fc gamma RI receptor motif at the start of CH2. An N-terminal glycosylation site and the peptide motif for complement C1q binding are present in CH2 of both isotypes. The hinge regions of gamma 1 and gamma 2 and predicted structures for ovine IgG1 and IgG2 have been modelled. Close apposition of Fab and Fc in IgG2 produces steric hindrance at the normally accessible Fab/hinge/Fc interface; the structural differences between the ruminant isotypes form a basis for understanding some of the differences in their effector properties.

Alternative splicing of neural-cell-adhesion molecule mRNA in human small-cell lung-cancer cell line H69

The neural-cell-adhesion molecule (NCAM) is expressed in all small-cell lung cancers (SCLC) and in approximately 20% of non-small-cell lung tumors (non-SCLC). These NCAM-positive lung tumors have a poor prognosis compared with NCAM-negative tumors. Multiple NCAM protein isoforms are expressed from a single-copy gene as a result of alternative splicing and/or post-translational modifications. Therefore, we studied the NCAM isoforms expressed in a human small-cell lung-cancer cell line, H69. NCAM mRNA transcripts of 7.2, 6.7, 4.3 and 4.0 were detected in these cells on Northern blots. Since the various NCAM isoforms may have different biological properties, we performed a more precise examination of NCAM mRNAs, using polymerase chain reactions (PCR) with primers flanking the various NCAM exon boundaries. The shortest alternatively spliced sequence that we found was the trinucleotide AAG located between exon 12 and 13 in the so-called hinge region of the NCAM protein. This AAG trinucleotide was present in the majority of the NCAM mRNAs. A second alternatively spliced 30 nt-exon VASE (immunoglobulin-variable domain-like alternatively spliced exon) was present in all NCAM transcript isoforms at the exon 7/exon 8 junction. VASE resulted in the insertion of 10 amino acids into the 4th immunoglobulin-like loop of the NCAM protein. Within the limits of the PCR methodology, no evidence for the presence of mRNA containing exon 15, encoding the glycosyl-phosphatidylinositol-linked (GPI-linked) NCAM isoform in H69 cells was obtained. Considering that H69 cells express 2 major NCAM protein classes (NCAM-180 and NCAM-140), and that the VASE and AAG alternative mRNA splice variants result in minor differences in protein sizes, at least 8 polypeptide isoforms of NCAM might be expressed in H69 cells that contribute to the binding interactions of NCAM.

Spontaneous deletions in Ig heavy chain genes: flanking sequences influence splice site selection

The cell line G403.4.7, isolated as a spontaneous variant of the MPC-11 derived myeloma G403.4, produces a truncated gamma 2b HC protein, but no light chain (LC), and a single gamma 2b specific transcript of 2.4kb. This gamma 2b transcript consists of the VDJ and CH1 exons, the CH1 to Hinge (Hi) intervening sequence (IVS) and HI exon, part of the IVS between the two membrane exons M1 and M2, and most of the membrane 3' untranslated (UT) region. Even though the mature mRNA contains intronic sequences, it is abundant in the cytoplasm. Analysis of the gamma 2b genomic organization reveals that this unusual transcript results in part from two genomic deletions of 2.5kb and 588bp and in part from an altered splicing pattern. This altered splicing pattern is probably a consequence of the sequence alterations resulting from the genomic deletions. Analysis of these events provides some interesting insights into the mechanism of splice site selection and the evolution of introns and exons.

Enhancement of complement activation and cytolysis of human IgG3 by deletion of hinge exons

The capacity to induce complement-mediated cell lysis is greatly enhanced by truncating the hinge of IgG3 through exon deletions. This was shown by establishing five new cell lines which secreted chimeric IgG3 molecules with specificity for the hapten 4-hydroxy-3-nitrophenacetyl (NP) and having 47,45,32,15, and 0 amino acid hinge regions (the wild-type IgG3 has 62 amino acids in the hinge). Efficient complement activation and complement-mediated cell lysis did not depend on a long total hinge or on a long 'upper' hinge (the stretch from the beginning of the hinge to the first inter-heavy chain S-S bond). On the contrary, the mutant having a 15 amino acid hinge element was up to 10 times more efficient in complement lysis than the wild type. Thus the complement-activation potential appeared to be down-regulated in the wild type. On the other hand, the mutant lacking the hinge altogether did not activate complement or induce complement-mediated cytolysis. These findings have to be taken into account when antibodies are designed for human therapy.

Genomic alterations in a case of alpha heavy chain disease leading to the generation of composite exons from the JH region

Human alpha heavy chain disease (HCD) is characterized by the presence in patient's serum of a short Ig alpha chain devoid of light chains. We analyzed the serum protein, the alpha HCD mRNA and the productive rearranged H chain gene from the leukemic cells of a new case (YAO) of alpha HCD. The abnormal YAO alpha 1 Ig was devoid of VH and CH1 domains and started at the beginning of the hinge region. The alpha HCD mRNA was shorter than normal alpha mRNA and the cDNA prepared from YAO mRNA encoded a leader sequence, an insert of 70 nucleotides and the CH2 and CH3 exons. The origin of the inserted sequence was assessed by cloning and sequence analysis of the alpha 1 productive gene. It started with a leader exon, a leader-VH intron and the first 11 bp of a VH exon. Then the VH region was deleted and replaced by a 19-nucleotide sequence that turned out to correspond to the 3' part of a modified JH5 exon. It was followed by a 221-bp sequence homologous to the JH5-psi JH3 intron and by an inserted sequence of unknown origin. The 3' part of this insertion and the remnant of a JH6 exon delineated a third exon that was followed by a relatively conserved JH6-C alpha intron. These two composite exons were flanked by splicing sites and accounted for the 70-nucleotide insert of the cDNA. The genomic nucleotide sequence also revealed a large deletion in the switch CH1 region which eliminated normal splicing sites and resulted in splicing of the third exon directly to the CH2 exon.

A human immunoglobulin IGHG3 allele (Gmb0,b1,c3,c5,u) with an IGHG4 converted region and three hinge exons

The five human IGHG genes consist of three constant domain exons plus one of or four hinge exon(s), the quadruplicated hinge region being characteristic of the IGHG3 gene. Besides this structural difference, the IGHG genes are polymorphic, as demonstrated by the restriction fragment length polymorphism and, at the protein level, by the Gm allotypic antigenic determinants. In this paper, we report the sequence of the G3m(b0, b1, c3, c5,u) IGHG3 allele, typical of the Black African populations and of populations with Negroid admixture, found in a homozygous Tunisian designated as LAT. We demonstrate that this G3 allele contains only three hinge exons instead of four (the probable result of an unequal crossing over) and that IGHG3 genes with triplicated hinge exons (and therefore encoding shorter gamma 3 chains) are present in healthy individuals from different populations. Moreover, we show that the LAT G3m (b0, b1, c3, c5, u) coding sequence results from the conversion, in the CH3 exon, of the G3m (b0, b1, b3, b4, b5, u, v) allele, the most frequent IGHG3 gene in the Negroid populations, by the homologous region of a IGHG4 gene. The structural features of the LAT IGHG3 allele, which are the lack of one hinge exon and its conversion by the IGHG4 gene, demonstrate that both crossing-over and gene conversion events occur in the evolution of the human IGHG genes.

Structure of bovine immunoglobulin constant region heavy chain gamma 1 and gamma 2 genes

Two bovine immunoglobulin constant region gamma heavy chain germline gene sequences are described. A gamma 1 gene was cloned from a lambda 2001 calf liver library screened with a human gamma 4 (pBRH4.1) probe and is contained in a 5.8 kb BamH1 hybridizing fragment. The gamma 2 gene was from an EMBL4 lambda library and is in a 6.6 kb BamH1 fragment. Each of these genes is arranged in four exons corresponding to the three CH domains and the hinge of gamma heavy chain genes; normal RNA splice and polyadenylation sites are present. The translated C-terminal peptide sequences of the genes match exactly the equivalent peptide sequences of bovine IgG1 and IgG2 heavy chains, identifying them as gamma 1 and gamma 2. The derived protein sequences reveal 96, 80 and 83% identity of amino acid residues between their CH1, CH2 and CH3 domains. Two adjacent cysteine residues encoded in the CH1 exons suggest that, as in rabbit gamma, an extra intra-chain disulphide bond occurs in the bovine gamma heavy chains. Significant DNA rearrangement in the hinge-CH2 region is evident in the bovine gamma 2 gene, with resultant deletion and substitution of amino acid residues in the lower hinge and N-terminal portion of the CH2 domain. The Fab-Fc interface of bovine IgG2 is predicted to be sterically blocked, relative to IgG1, which has implications for effector differences between the bovine gamma subclasses.

Isolation and characterization of the mouse CD8 beta-chain (Ly-3) genes. Absence of an intervening sequence between V- and J-like gene segments

We have isolated and determined the nucleotide sequence and genomic organization of the genes encoding Ly-3.1 and Ly-3.2. These genes span approximately 14 kb on chromosome 6 and consist of six exons and five introns. The exons correlate roughly with the putative functional domains, namely, a leader exon, a variable and joining region-like exon, a hinge region-like exon, a transmembrane exon, and two intracytoplasmic exons. There is no intervening sequence between V- and J-like gene segments, indicating that rearrangement is not necessary for the expression of the Ly-3 gene. In the 5'-flanking region there is no "TATA" box nor "CAAT" box; however, three "GC" boxes are located upstream of the ATG initiator codon. There are short stretches of sequence homologous to 5'-flanking sequences of the Ly-2 gene. In addition, the sequences CTCTGTGGCA at -748 exhibits homology to the enhancer core sequence of the human Ig H chain and TCR genes. Comparison of the nucleotide sequence corresponding to the extracellular portion between Ly-3.1 and Ly-3.2 revealed a single base difference which results in an amino acid substitution. Therefore it is likely that this amino acid difference is responsible for the previously defined Ly-3 allotypes.

Protein Rou. A human IgA hybrid

Protein Rou is a human IgA2 myeloma protein that carries the isoallotype marker n A2m(2). Partial amino acid sequence of its H chain (alpha) shows that the hinge region and the CH2 domain are homologous to alpha 2-chain and the CH1 and the CH3 domains homologous to alpha 1. Moreover, the CH1 domain contains the H-L disulfide bond identical to alpha 1. It is concluded that Rou H chain is a hybrid molecule caused by a recombination between alpha 1 and alpha 2 genes. The recombination event occurred between alpha 1-exon 1 and alpha 2-exon hinge and corresponds to position 222-223 of the alpha-chain.

DNA sequence analysis of two bovine immunoglobulin CH gamma pseudogenes

A bovine calf liver DNA library in lambda 2001 bacteriophage has been screened with a human Ig gamma 4 heavy-chain constant-region gene probe. Four hybridizing clones have been identified, and the DNA sequences in two of these, which have high homology with CH gamma genes, are reported here. Within the bovine sequences, four separate exons can be identified, corresponding to the three CH domains and the hinge of gamma heavy-chain genes. Both of these genes contain atypical sequences around one or more of their exon/intron boundaries with consequent loss of splice sites, indicating that these are probably gamma pseudogenes. One sequence codes for a C-terminal peptide which matches the 18-mer C-terminal heavy-chain peptide of bovine serum IgG2, the other encodes a C-terminal peptide unknown in the bovine. These results suggest that evolutionary duplication of CH gamma genes has occurred in the bovine.

Isolation and characterization of the gene for the murine T cell differentiation antigen and immunoglobulin-related molecule, Lyt-2

We present here the sequence of the 5310 base pair Hind III-cleaved genomic DNA segment that includes the gene for the Lyt-2, a murine differentiation antigen expressed on most immature T lymphocytes as well as the cytotoxic suppressor T cell subset. We also present the complete intron/exon structure of Lyt-2. There are five exons: a fused leader and immunoglobulin variable region like exon, a hinge region exon, a transmembrane exon and two alternatively spliced intracytoplasmic exons (alternative splicing of these exons yields the 38 kDa alpha and 34 kDa alpha' Lyt-2 polypeptides). The promotor region contains a "TATA" box and sequences homologous to the putative immunoglobulin transcriptional control elements cd/pd. S1 protection analysis reveals that thymocytes, T cells from lymph nodes, and a Lyt-2 transfectant obtained by introduction of total genomic DNA have the same initiation site. In the 3' region, there is a polyadenylation signal sequence after a 700 bp long 3' untranslated region.

A gamma 3 hinge region probe: first specific human immunoglobulin subclass probe

We report the first specific human immunoglobulin subclass probe which was obtained by subcloning the gamma 3 hinge region. This specific gamma 3 probe allowed us to identify with certainty the C gamma 3 gene on Southern genomic blots, to describe the first C gamma 3 restriction fragment length polymorphism (EZZ gamma 3 RF) and to show that an IgG3 selective deficiency, previously described serologically, was not due to a deletion of the C gamma 3 gene. Such a probe should be particularly useful for screening libraries from individuals with IgG3 immunodeficiencies or presenting unusual C gamma 3 genes and, consequently, for studying the C gamma gene evolution.