Rearrangement of antigen receptor genes is defective in mice with severe combined immune deficiency

A process unique to lymphocyte differentiation is the rearrangement of genes encoding antigen-specific receptors on B and T cells. A mouse mutant (C.B-17scid) with severe combined immune deficiency, i.e., that lacks functional B and T cells, shows no evidence of such gene rearrangements. However, rearrangements were detected in Abelson murine leukemia virus-transformed bone marrow cells and in spontaneous thymic lymphomas from C.B-17scid mice. Most of these rearrangements were abnormal: approximately 80% of Igh rearrangements deleted the entire Jh region, and approximately 60% of TCR beta rearrangements deleted the entire J beta 2 region. The deletions appeared to result from faulty D-to-J recombination. No such abnormal rearrangements were detected in transformed tissues from control mice. The scid mutation may adversely affect the recombinase system catalyzing the assembly of antigen receptor genes in developing B and T lymphocytes.     

T cell differentiation model based on the expression of T cell receptor chains and genes--study in the human leukemia/lymphoma cell lines

A total of 33 human leukemia/lymphoma cell lines were classified into 4 groups with respect to the pattern of cell membrane (sm) expression of the CD3 and T cell receptor (TCR) molecules; (i) smCD3+TCR alpha beta (16 cell lines), (ii) smCD3+TCR beta delta (1 cell line), (iii) smCD3+TCR gamma delta (3 cell lines) amd (iv) smCD3-TCR- (13 cell lines), respectively. Using monoclonal antibodies (MoAbs) specific to CD3 (NU-T3), TCR alpha chain (alpha F1), TCR beta chain (beta F1), and TCR gamma chain (C gamma M1), respectively, cytoplasmic (cy) expression of these molecules was determined by immunofluorescence test. Expression of cyCD3 was present in all cell lines regardless of groups. In group (i), all 16 cell lines expressed both TCR alpha and beta chains. While only TCR beta chain was expressed in group (ii), TCR gamma chain was expressed in all 3 cell lines of group (iii). One (PEER) of the three in group (iii) expressed TCR beta chain as well. In group (iv), we found 8 cell lines with cyTCR alpha expression, 11 cell lines with cyTCR beta expression, and 10 cell lines with cyTCR gamma expression, respectively. For TCR genes, except 1 cell line all cell lines were found to present rearranged C beta gene and its mRNA, including all 3 TCR gamma/delta cell lines of group (iii). One of the TCR alpha beta cell lines exhibited rearranged C delta and J delta genes as well as its mRNA. Two cell lines of the 13 CD3-TCR- of group (iv) exhibited rearranged C delta and J delta and its mRNA. An NK-like activity and IL-2 production were induced in the TCR beta delta and gamma delta cell lines [group (ii) and (iii)] by treatment with PHA and PMA.     

Human T cell gamma-chain gene rearrangements in acute lymphoid and nonlymphoid leukemia: comparison with the T cell receptor beta-chain gene

Rearrangement of germ-line genes coding for T and B cell antigen receptor molecules is an early event in lymphoid development which eventually leads to the generation of clonal diversity in receptor-positive lymphocytes. Three T cell-associated rearranging genes have been described. Two, T alpha and T beta, code for the two polypeptide chains that form the T cell receptor heterodimer. The function of the third gene, the gamma-gene (T gamma), is not known. To learn more about the behavior of T gamma during lymphoid ontogeny, we compared rearrangement of T gamma and T beta genes in leukemic cells arrested at varied stages of lymphoid and myeloid development. We analyzed 38 fresh cell lines and 15 established cell lines from a total of 53 leukemic patients. Cells were immunophenotyped with a panel of monoclonal antibodies recognizing T-, B-, or myeloid-associated surface markers. Sixteen T-lineage cases were studied; 15 displayed both T beta and T gamma rearrangements. The exception (germ-line for T beta and T gamma) was an immature CD2(T11)+, CD3(T3)-, CD7(3A1)+, CD1(T6)+, CD5(T101)+ phenotype. Fourteen non-T non-B leukemias were analyzed; eight were germ-line for both T beta and T gamma, four had rearrangements involving both T beta and T gamma, and two were germ-line for T beta and rearranged to T gamma. Four cases with acute biphenotypic leukemia were studied; two had rearrangements of T beta and T gamma, and two were germ-line for both genes. Cells from nonlymphocytic leukemias were studied in 19 cases. All were found to be germ-line for both T beta and T gamma. Fifty-one of 53 genomic DNA samples were concordant for T gamma and T beta rearrangement. These results indicate that rearrangement of T gamma can occur in leukemic cells of B cell as well as T cell precursor origin, as has been reported previously for T beta.     

The T cell receptor beta locus of the channel catfish,Ictalurus punctatus,reveals unique features

Previously, a series of clonal alloantigen-dependent T cell lines established from the channel catfish revealed distinctly different TCR beta rearrangements. Here, a follow-up study of the junctional diversity of these TCR gene rearrangements focuses on characterization of the genomic organization of the TCRB locus. Surprisingly, a total of 29 JB genes and two substantially different CB genes were identified downstream of a single DB gene. This is in contrast to the situation in mammals, where two clusters of a DB gene, six or seven JB genes, and a CB gene are found in tandem. The catfish CB genes are approximately 36% identical at the amino acid level. All 29 catfish JB gene segments appear functional. Thirteen were used in the 19 cDNAs analyzed, of these eight were used by the 11 catfish clonal alloantigen-dependent T cell lines. As might be expected, CDR3 diversity is enhanced by N-nucleotide additions as well as nucleotide deletions at the V-D and D-J junctions. Taken together, compared with that in mammals, genomic sequencing of the catfish TCR DB-JB-CB region reveals a unique locus containing a greater number of JB genes and two distinct CB genes.     

Abnormal recombination of Igh D and J gene segments in transformed pre-B cells of scid mice

Studies of Ig and TCR genes in transformed lymphocytes of scid mice have revealed aberrant DNA rearrangements. Here we present a more detailed analysis of the Igh gene recombination in nine scid pre-B cell lines transformed by Abelson murine leukemia virus. We found 85% of the rearranged Igh alleles to contain abnormal Dh-Jh deletions of varying size. All of these deletions encompassed Jh elements and extended into the Igh enhancer region, occasionally involving the switch (S) region of the C mu gene. Some of these rearrangements removed most of the Dh elements, but none appeared to extend to the Vh genes. DNA sequence analysis of the two abnormally rearranged Igh alleles in one pre-B cell line showed that no Dh or Jh coding sequences were retained at the recombination sites though heptamer-like (CACTGTG) recognition signal sequences were present in the absence of nonamer (GGTTTTTGT) recognition signal sequences. These results imply that a deregulated recombinase activity may be responsible for the abnormal Dh-Jh deletions and the absence of Vh-Dh joining in established lines of Abelson murine leukemia virus-transformed scid pre-B cells.     

Rearrangement and expression of T-cell antigen receptor genes in human T-lymphocyte tumor lines and normal human T-cell clones: evidence for allelic exclusion of Ti beta gene expression and preferential use of a J beta 2 gene segment.

The gene encoding the beta chain of the human T-cell receptor for antigen is composed of variable (V), diversity (D), joining (J), and constant (C) gene segments which undergo specific rearrangements during T-lymphocyte ontogeny. Southern blot analyses of seven human T-cell tumor lines and normal human T-lymphocyte clones revealed that most of these T-cell lines rearrange their Ti beta genes differently. The T-cell tumor line HPB-MLT rearranges and transcribes both of its Ti beta genes. Cloning and sequencing of the Ti beta cDNAs corresponding to these rearrangements revealed that one of the rearranged Ti beta genes is defective, while the other is functional and corresponds to the Ti beta protein expressed on the surface of these cells. Thus, this cell line displays a pattern of allelic exclusion of Ti beta gene expression. A comparison of four C beta 2-containing Ti beta cDNAs from three different cell lines revealed that three of the four utilize the same J beta 2.5 gene segment joined to different D beta and V beta genes, suggesting that there may be preferential use of this J gene during J beta 2 rearrangements. Hybridization analyses with probes for the alpha and beta genes of the T-cell receptor and the T-cell-specific T gamma gene revealed that HPB-MLT cells appear to express approximately equivalent amounts of RNA corresponding to each of the rearranged Ti alpha and Ti beta genes. However, they express a much lower level of T gamma RNA.     

Identification and expression of the Tla region gene T11b and its Qa-like product

In spite of the large number of class I genes in the Qa-Tla region of the H-2 complex, only few membrane-bound Qa and TL Ag have been identified. We show that one of the Qa-Tla region genes, the T11b gene, is transcribed in lymphoid cells, lymphoma cell lines, teratocarcinoma cell lines, and L cells transfected with the cloned T11b gene. The T11b gene potentially encodes a polypeptide with normal class I characteristics. The product as present at the cell surface of L cells transfected with the cloned T11b gene, is a sialylated protein of m.w. 41,000, associated with beta 2-microglobulin. This T11b Ag shares epitopes with H-2K and H-2D molecules of various haplotypes and with Qa-2 molecules, but has distinct biochemical properties. RFLP analysis revealed that the T11b gene is found in mice of the Tlab and Tlaf haplotype. Genes homologous to, but distinct from, T11b (allelic or duplicated) are present in all Tla haplotypes tested.     

Assignment of the human dihydrofolate reductase gene to the q11----q22 region of chromosome 5.

Cells from a dihydrofolate reductase-deficient Chinese hamster ovary cell line were hybridized to human fetal skin fibroblast cells. Nineteen dihydrofolate reductase-positive hybrid clones were isolated and characterized. Cytogenetic and biochemical analyses of these clones have shown that the human dihydrofolate reductase (DHFR) gene is located on chromosome 5. Three of these hybrid cell lines contained different terminal deletions of chromosome 5. An analysis of the breakpoints of these deletions has demonstrated that the DHFR gene resides in the q11----q22 region.     

Breakpoint junctions of chromosome 9p deletions in two human glioma cell lines.

Interstitial deletions of the short arm of chromosome 9 are associated with glioma, acute lymphoblastic leukemia, melanoma, mesothelioma, lung cancer, and bladder cancer. The distal breakpoints of the deletions (in relation to the centromere) in 14 glioma and leukemia cell lines have been mapped within the 400 kb IFN gene cluster located at band 9p21. To obtain information about the mechanism of these deletions, we have isolated and analyzed the nucleotide sequences at the breakpoint junctions in two glioma-derived cell lines. The A1235 cell line has a complex rearrangement of chromosome 9, including a deletion and an inversion that results in two breakpoint junctions. Both breakpoints of the distal inversion junction occurred within AT-rich regions. In the A172 cell line, a tandem heptamer repeat was found on either side of the deletion breakpoint junction. The distal breakpoint occurred 5' of IFNA2; the 256 bp sequenced from the proximal side of the breakpoint revealed 95% homology to long interspersed nuclear elements. One- and two-base-pair overlaps were observed at these junctions. The possible role of sequence overlaps, and repetitive sequences, in the rearrangement is discussed.     

T cell receptor genes and T cell development in virus-transformed early T cell lines

We have derived T cell lines from mice inoculated with Gross leukemia virus, which appear to represent early T cell developmental stages and to reflect normal T cell development. These cell lines may provide a breakthrough in the study of T cell development as Abelson transformants have done for the study of B cell development. Analysis of the TCR gene expression in these cell lines reveals that the sequence of rearrangement and expression of each TCR gene is not strictly ordered. Expression of RNA for the TCR alpha and -beta genes appears to be coordinated with rearrangement at the alpha and beta loci. This is not the case for gamma gene expression. Availability of the homogeneous populations of cells represented in these cells lines allows for a more detailed molecular analysis of T cell development than was previously possible.     

Murine AIDS superantigen reactivity of the T cells bearing V beta 5 T cell antigen receptor.

A B cell line, B6-1710, that expresses the defective virus known to induce murine AIDS stimulates a large fraction of nonprimed splenic T cells. Analysis of the T cell population responding to the B6-1710 for TCR V beta-chain usage revealed that, in addition to the previously reported V beta 5-chain-positive T cells, T cells bearing V beta 11 and V beta 12 are also specifically enriched. We have established V beta 5+ T cell lines, clones, and hybridomas expressing identical TCR with different CD4/CD8 phenotypes and demonstrated that T cell reactivity to B6-1710 is, although not absolute, dependent on the presence of CD4 molecules. Further analysis of T cell hybridomas with known J beta-chain usage revealed that D beta- and J beta-chain usage do not play crucial roles in T cell reactivity to B6-1710 B cells. However, T cell hybridomas derived from TCR-V beta gene transgenic mice were found to be heterogeneous for their reactivity to B6-1710, suggesting that the V alpha-chains associating with the transgenic V beta-chain determine T cell responsiveness to B6-1710. These data clearly demonstrate that T cell reactivity to a murine AIDS virus expressing B cell line resembles that previously reported for Mls-like superantigens.     

Effects of hyperthermia on the in vitro antiproliferative activities of HuIFN-alpha, HuIFN-beta, and rHuIFN-gamma employed separately and in combination

The relative enhancing effects of hyperthermia on the three types of interferon were evaluated in cloning studies for three human cell lines: G-361 malignant melanoma cells, WISH ammion cells, and AGS stomach adenocarcinoma cells. Hyperthermia enhanced the antiproliferative activity of rHuIFN-gamma against each of the three cell lines and the levels of enhancement by hyperthermia were seen to increase with increasing concentrations of rHuIFN-gamma. The maximum observed levels of enhancement of rHuIFN-gamma activity by hyperthermia varied from cell line to cell line. However, when the relative sensitivities of the cell lines to rHuIFN-gamma were taken into account, the levels of enhancement of rHuIFN-gamma antiproliferative activity by hyperthermia were seen to be similar for each of the cell lines, indicating that hyperthermia consistently enhanced rHuIFN-gamma antiproliferative activity. Hyperthermia did not consistently enhance the antiproliferative activities of HuIFN-alpha and HuIFN-beta. Further studies indicated that hyperthermia enhanced by approximately 6-fold the antiproliferative effects of combinations of rHuIFN-gamma with HuIFN-alpha and HuIFN-beta. The results support the possibility that a combination treatment protocol of hyperthermia and interferon administration (particularly HuIFN-gamma or combinations of HuIFN-gamma with HuIFN-alpha or HuIFN-beta) may provide an enhanced antitumor effect in man.