Expression of the T-cell receptor gamma-chain gene products on the surface of peripheral T cells and T-cell blasts generated by allogeneic mixed lymphocyte reaction

Influenza A Virus Hemagglutinin and Other Pathogen Glycoprotein Interactions with NK Cell Natural Cytotoxicity Receptors NKp46, NKp44, and NKp30

Natural killer (NK) cells are part of the innate immunity repertoire, and function in the recognition and destruction of tumorigenic and pathogen-infected cells. Engagement of NK cell activating receptors can lead to functional activation of NK cells, resulting in lysis of target cells. NK cell activating receptors specific for non-major histocompatibility complex ligands are NKp46, NKp44, NKp30, NKG2D, and CD16 (also known as FcγRIII). The natural cytotoxicity receptors (NCRs), NKp46, NKp44, and NKp30, have been implicated in functional activation of NK cells following influenza virus infection via binding with influenza virus hemagglutinin (HA). In this review we describe NK cell and influenza A virus biology, and the interactions of influenza A virus HA and other pathogen lectins with NK cell natural cytotoxicity receptors (NCRs). We review concepts which intersect viral immunology, traditional virology and glycobiology to provide insights into the interactions between influenza virus HA and the NCRs. Furthermore, we provide expert opinion on future directions that would provide insights into currently unanswered questions.

Septin 9 isoforms promote tumorigenesis in mammary epithelial cells by increasing migration and ECM degradation through metalloproteinase secretion at focal adhesions

The cytoskeletal interacting protein Septin 9 (SEPT9), a member of the septin gene family, has been proposed to have oncogenic functions. It is a known hot spot of retroviral tagging insertion and a fusion partner of both de novo and therapy-induced mixed lineage leukemia (MLL). Of all septins, SEPT9 holds the strongest link to cancer, especially breast cancer. Murine models of breast cancer frequently exhibit Sept9 amplification in the form of double minute chromosomes, and about 20% of human breast cancer display genomic amplification and protein over expression at the SEPT9 locus. Yet, a clear mechanism by which SEPT9 elicits tumor-promoting functions is lacking.

To obtain unbiased insights on molecular signatures of SEPT9 upregulation in breast tumors, we overexpressed several of its isoforms in breast cancer cell lines. Global transcriptomic profiling supports a role of SEPT9 in invasion. Functional studies reveal that SEPT9 upregulation is sufficient to increase degradation of the extracellular matrix, while SEPT9 downregulation inhibits this process. The degradation pattern is peripheral and associated with focal adhesions (FA), where it is coupled with increased expression of matrix metalloproteinases. SEPT9 overexpression induces MMP upregulation in human tumors and in culture models and promotes MMP3 secretion to the media at FAs. Downregulation of SEPT9 or chemical inhibition of septin filament assembly impairs recruitment of MMP3 to FAs. Our results indicate that SEPT9 promotes upregulation and both trafficking and secretion of MMPs near FAs, thus enhancing migration and invasion of breast cancer cells.

Evolution and function of the TCR Vgamma9 chain repertoire: It's good to be public

Lymphocytes expressing a T cell receptor (TCR) composed of Vgamma9 and Vdelta2 chains represent a minor fraction of human thymocytes. Extrathymic selection throughout post-natal life causes the proportion of cells with a Vgamma9-JP rearrangement to increase and elevates the capacity for responding to non-peptidic phosphoantigens. Extrathymic selection is so powerful that phosphoantigen-reactive cells comprise about 1 in 40 circulating memory T cells in healthy adults and the subset expands rapidly upon infection or in response to malignancy. Skewing of the gamma delta TCR repertoire is accompanied by selection for public gamma chain sequences such that many unrelated individuals overlap extensive in their circulating repertoire. This type of selection implies the presence of a monomorphic antigen-presenting molecule that is an object of current research but remains incompletely defined. While selection on a monomorphic presenting molecule may seem unusual, similar mechanisms shape the alpha beta T cell repertoire including the extreme examples of NKT or mucosal-associated invariant T cells (MAIT) and the less dramatic amplification of public Vbeta chain rearrangements driven by individual MHC molecules and associated with resistance to viral pathogens. Selecting and amplifying public T cell receptors whether alpha beta or gamma delta, are important steps in developing an anticipatory TCR repertoire. Cell clones expressing public TCR can accelerate the kinetics of response to pathogens and impact host survival.

Activation of murine epidermal V gamma 5/V delta 1-TCR(+) T cell lines by Glu-Tyr polypeptides

The physiologic role of gamma delta-T-cell-receptor-bearing cells and the T cell receptor ligands that they recognize is still poorly understood. Previous studies have suggested that one possible antigen for gamma delta-TCR(+) cells is the random copolymer poly-glutamic acid-tyrosine (poly-Glu-Tyr), because poly-Glu-Tyr-reactive gamma delta-TCR(+) hybridoma cells were produced from poly-Glu-Tyr-immunized mice. We have found, however, that clonal V gamma 5/V delta 1-TCR(+) epidermal T cell lines from nonimmune mice also respond to poly-Glu-Tyr by producing cytokines. Other amino acid homopolymers, copolymers, and tripolymers were not stimulatory for the V gamma 5/V delta 1-TCR(+) epidermal T cells, except for poly-glutamic acid-alanine-tyrosine (poly-Glu-Ala-Tyr). Of the poly-Glu-Tyr and poly-Glu-Ala-Tyr polymers, only those that contained Glu and Tyr in an equimolar ratio were stimulatory. The cytokine interleukin-2 was strictly required for the responses to poly-Glu-Ala-Tyr, whereas the responses to poly-Glu-Tyr were merely enhanced with interleukin-2. The response to poly-Glu-Tyr was also enhanced by crosslinking CD28 molecules with plate-bound anti-CD28 crosslinking antibody. This finding suggests that the poly-Glu-Tyr response has a partial dependence on CD28-mediated costimulation, a characteristic of TCR-dependent responses. Consistent with this observation, V gamma 5/V delta 1-TCR-loss variants of the epidermal T cell line could no longer respond to poly-Glu-Tyr. The unpredicted responses of epidermal gamma delta-TCR(+) T cells to poly-Glu-Tyr and poly-Glu-Ala-Tyr demonstrate that the functions of these cells potentially can be triggered by peptidic ligands, probably through a TCR-mediated process.

Inflammation Alone Evokes the Response of a TCR-Invariant Mouse γδ T Cell Subset

Whether γδ T lymphocytes respond to microbial Ags or to inducible host Ags remains a matter of controversy. Using several different disease models and mouse strains, we and others have seen that Vγ6/Vδ1 γδ T cells preferentially increase among the γδ T cells infiltrating inflamed tissues. However, it was not clear whether bacteria are necessary to bring about this response. Therefore, we have reexamined this question using a disease model in which inflammation is induced by a purely autoimmune process involving no bacteria, bacterial products, or other foreign material: testicular cell-induced autoimmune orchitis. Using this model we found that γδ T cells were still plentiful among the infiltrating T lymphocytes, being 9- to 10-fold more prevalent than in spleen, and that Vγ6/Vδ1+ cells again represented the predominant γδ T cell type. This finding shows that the response of the Vγ6/Vδ1+ subset does not, in fact, depend upon the presence of bacteria or bacterial products. The stimulus triggering the response of the Vγ6/Vδ1 γδ T cells appears to be neither foreign nor organ-specific in origin, but instead consists of a self-derived host Ag or signal induced during the inflammatory process.

Normal macrophage functions, but impaired induction of gamma delta T cells, at the site of bacterial infection in CD45 exon 6-deficient mice

We investigated the protective functions of macrophages and gamma delta T cells in adult CD45 exon 6-deficient (CD45 -/-) mice against an intraperitoneal (i.p.) infection with Listeria monocytogenes. gamma delta T cells are preferentially localized in the spleen, liver, and intraperitoneal cavity of the adult CD45-/- mice. Increased numbers of gamma delta T cells were observed after i.p. infection with L. monocytogenes in the peritoneal cavity of C57BL/6 (CD45 +/+) mice but not in CD45 -/- mice. The gamma delta T cells showed predominant usage of V delta 5 and V delta 6 rearranged to J delta 1 in the infected CD45 -/- mice which are the same as those used by resident gamma delta T cells of noninfected CD45 +/+ and CD45 -/- mice. Furthermore, we analyzed the protective abilities of the CD45 -/-, CD45 +/+, and gamma delta T cell-depleted mice at the early stage of the listerial infection. The numbers of bacteria in the spleens and livers of the CD45 -/- mice 5 days after the listerial infection were almost ten times larger than those in the CD45 -/- and gamma delta T cell-depleted CD45 +/+ mice. Macrophages showed normal antigen presentation, nitric oxide production and bactericidal activity for L. monocytogenes despite their lacking CD45 surface expression, suggesting that CD45-negative macrophages have a minimal influence on the increased bacterial multiplication in the CD45-/- mice. These results suggest that the gamma delta T cells are induced by the bacterial infection in a CD45-dependent manner, and that unresponsiveness of the gamma delta T cells results in only weak protection against L. monocytogenes in CD45 -/- mice.

Functional difference between Thy-1-positive and Thy-1-negative gamma delta T cells induced by Escherichia coli infection in mice

There is an increase in number of gamma delta T cells in the peritoneal cavity after intraperitoneal (i.p.) inoculation with Escherichia coli. The E. coli-induced gamma delta T cells in C3H/He mice contain a large amount of Thy-1-negative population in addition to the Thy-1-positive population. We investigated the difference between the Thy-1-positive and the Thy-1-negative gamma delta T cells. Although it was found that only up to 4% of the gamma delta T cells on day 5 after infection were in cycling phase, and that the gamma delta T cells did not proliferate by immobilized anti-T-cell receptor (TCR) gamma delta monoclonal antibody stimulation, the gamma delta T cells proliferated in the presence of interleukin-2 (IL-2) and IL-7. The Thy-1-negative gamma delta T cells showed higher proliferative response compared with the Thy-1-positive gamma delta T cells. Furthermore, the Thy-1-negative gamma delta T cells showed lower IFN-gamma mRNA expression than the Thy-1-positive gamma delta T cells. On the other hand, both the Thy-1-positive and Thy-1-negative gamma delta T cells predominantly expressed V gamma 1, V gamma 4, V gamma 5, V gamma 6 and V delta 1, and no difference of V region usage was detected between them. These results suggest that functions of Thy-1-positive gamma delta T cells differ from Thy-1-negative gamma delta T cells although Thy-1-positive and Thy-1-negative gamma delta T cells may have similar V region repertoire and, possibly, similar antigen specificity.

Amino acid substitutions in the floor of the putative antigen-binding site of H-2T22 affect recognition by a gamma delta T-cell receptor

We have previously identified a self-reactive gamma delta T-cell clone (KN6) specific for the H-2T region gene product T22b. Now we have investigated by an in vitro mutagenesis analysis of the T22b gene the possibility that the interaction between the KN6 gamma delta T-cell receptor and T22b involves a peptide. The results demonstrate that mutations at the floor of the putative antigen-binding groove of T22b affect recognition by the gamma delta T-cell receptor. Furthermore, we have shown that KN6 cells react with cells that are deficient in the class I peptide transporter TAP1/TAP2. These results suggest that peptide is involved in the interaction of the KN6 T-cell receptor with T22 and that loading of T22 with the putative peptide is TAP1/TAP2-independent.

Surface expression of two distinct functional antigen receptors on human gamma delta T cells

Lymphocytes recognize antigens with highly variable heterodimeric surface receptors. Although four distinct antigen receptors could in principle be produced by any lymphocyte, only one functional combination of receptor chains has thus far been found expressed on their surface. Examination of human gamma delta T cells revealed a population that violated this rule by expressing on their surface two distinct functional gamma delta T cell receptors (TCRs) that used different TCR gamma gene alleles. Thus, current models for T cell clonal selection may need modification, and a possible escape mechanism for autoreactive TCRs is suggested.

Characterization of T-cell receptor gamma delta T cells appearing at the early phase of murine Listeria monocytogenes infection

It has been shown that T-cell receptor (TcR) gamma delta + CD4- CD8- T cells increase in number and have an important role in early protection in murine Listeria monocytogenes infection. In this report, to characterize further the phenotype of the gamma delta T cells in listeriosis, we analysed V region gene usage and in vitro antigen recognition of the TcR gamma delta T cells in the peritoneal cavity of mice at the early phase after i.p. infection with a sublethal dose of L. monocytogenes. The gamma delta T cells predominantly expressed V delta 6 which has been reported to be expressed by TcR gamma delta-bearing foetal thymocyte hybridomas specific to mycobacterial and self heat-shock protein (hsp) 60. These early appearing CD3+ CD4- CD8- T cells in Listeria-infected mice, which were reported to be TcR gamma delta T cells, increased in proportion and in size by in vitro stimulation with recombinant hsp 60 from Mycobacterium bovis and purified protein derivative from M. tuberculosis but not by stimulation with heat-killed L. monocytogenes. A 65,000 MW molecule was detected in the lysate of viable L. monocytogenes but not in the lysate of heat-killed L. monocytogenes by a monoclonal antibody (mAb) raised against mycobacterial hsp 60. These results suggest that the V delta 6-bearing peripheral gamma delta T cells are activated by recognizing listerial hsp 60 expressed by viable L. monocytogenes. The hsp 60-reactive V delta 6-bearing T cells may have an important role in protection against L. monocytogenes and other parasites that express hsp 60 at high level.

Novel excision products of T cell receptor gamma gene rearrangements and developmental stage specificity implied by the frequency of nucleotide insertions at signal joints

We have cloned circular DNA excised by T cell receptor (TcR) gamma 1, gamma 2 and gamma 3 gene rearrangements in fetal and adult mouse thymocytes. Circular DNA contained a signal joint reciprocal to the genomic V-J coding joint. Although signal joints without nucleotide insertions are common in immunoglobulin (Ig) and TcR gene rearrangements, the signal joint of gamma found in adult thymocytes contained non-germ-line element (N) insertions at high frequency, while no insertions were found in fetal thymocytes. Thus developmental stage specificity of TcR gamma gene rearrangements is faithfully reflected on the signal joint of excision products. In addition, examination of gamma gene excision products revealed circular DNA products of TcR gamma-alpha transrearrangements, but no evidence of V gamma gene replacement in a rearranged segment.

Intestinal intraepithelial lymphocyte T cells are resistant to Ipr gene-induced T cell abnormalities

The mucosal immune system of the gastrointestinal (GI) tract consists of Peyer's patches (PP), which are IgA inductive sites, and more diffuse effector regions which include cells in the intraepithelial lymphocyte (IEL) compartment. Since autoimmune MRL lpr/lpr (MRL/lpr) mice develop a proliferating CD3+, CD4-, CD8- (double negative; DN), B220+ T cell subset in systemic lymphoid tissue, we have initiated studies to determine the distribution of CD3+, DN, B220+ T cells (B220+ T cells or lpr/lpr T cells) in the GI immune system. Specifically, we examined T cell subsets separated according to expression of CD4, CD8, Thy-1, B220, alpha/beta T cell receptor (TcR) and gamma/delta TcR in PP and IEL of MRL/lpr mice at 6, 12 and 21 weeks of age. Increased numbers of CD3+ T cells were noted in both PP and spleen of 12- and 21-week-old mice in which the development of autoimmune disorders were also evident. However, normal numbers of CD3+ IEL T cells were seen in MRL/lpr mice in all three age groups tested. When the presence of T cell lymphadenopathy was examined in both IgA inductive and effector tissues, the PP followed the B220+ T cell pattern seen in the spleen, where approximately 30%-50% of CD3+ T cells in the PP of 12- and 21-week-old MRL/lpr mice expressed the phenotype of lpr/lpr T cells and greater than 90% were alpha/beta TcR+. On the other hand, B220+ T cells had not developed in PP or spleen of 6-week-old MRL/lpr mice. Of interest was the finding that IEL from lpr/lpr homozygous mice did not contain B220+ T cells in any age group tested. In this regard, the IEL of MRL/lpr mice comprised an identical pattern and frequency of CD4-/CD8+, CD4+/CD8-, DN and CD4+/CD8+ (double positive, DP) T cell subsets as their normal counterparts (i.e. MRL +/+, BALB/c and C3H/HeN mice) which consisted of approximately 75%, approximately 7.5%, approximately 7.5% and approximately 10%, respectively. Further, Thy-1, gamma/delta TcR and alpha/beta TcR expression in these four subsets of MRL/lpr IEL were very similar to normal mice. These results suggest that the intestinal IEL compartment is minimally affected by the lpr/lpr mutation which induces T cell abnormalities and indicate that B220+ T cells do not preferentially home to IEL. Further, our results support the concept that IEL T cells develop as a separate T cell lineage from thymus-derived cells.

IL-2-dependent murine T-cell lines and clones expressing gamma/delta T-cell antigen receptors. I. Functional and biochemical characterization

We have developed two stable IL-2-dependent T-cell lines designated AKV-I and AKV-N from the enlarged spleens, respectively, of an AKV1 and an NFS mouse. Immunofluorescence staining with the appropriate monoclonal antibodies revealed that cells of the AKV-I cell line were alpha beta TCR-CD3+CD4-CD5-CD8+CD25+, whereas cells of the AKV-N cell line were alpha beta TCR-CD3+CD4-CD5+CD8-CD25+. A number of T-cell clones were developed from the AKV-I or AKV-N T-cell lines by limiting dilution and analysed by immunofluorescence. All clones tested were alpha beta TCR-CD3+CD4-CD25+. Certain T-cell clones expressed the CD5 antigen, whereas others expressed the CD8 antigen. The AKV-I cell line responded by proliferation to rIL2, rIL4, phorbol myristate acetate (PMA), PMA plus IL-4 and PMA plus PHA or Con A. In contrast, the AKV-N cell line did not respond to rIL-4 or rIL-4 plus PMA and exhibited only a modest proliferative response to PMA alone. Both AKV-I and AKV-N T-cell lines as well as a large number of T-cell clones examined were able to lyse cells of the PU5-IR murine cell line in the presence of the anti-CD3 (clone 145-2C11) MoAb, demonstrating their ability to mediate cytotoxicity in this system. Biochemical analysis of both AKV lines and a number of clones by immunoprecipitation with the anti-CD3 MoAb, followed by one-dimensional (either non-reducing or reducing) or two-dimensional (non-reducing/reducing) SDS-PAGE, revealed that the AKV lines and clones expressed a disulphide-linked dimer. Under non-reducing conditions, a band in the range of 75-85 kDa was observed and upon reduction it was resolved into two discrete polypeptide chains of 43-44 kDa and 48 kDa in certain AKV-I cells or 38 kDa and 42 kDa in certain AKV-N cells. In other T-cell clones or lines a broad band of 42-47 kDa was observed in AKV-I cells or 38-45 kDa in AKV-N cells. These results suggest the presence of different forms of disulphide-linked dimers on these cells. Northern blotting analysis using probes specific for the constant regions of the alpha-, beta-, gamma- and delta-chains of the T-cell antigen receptor revealed that all the AKV cell lines or clones tested expressed full-length alpha-, gamma- and delta-chain mRNA, whereas beta-chain mRNA was absent.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction, specificity and elimination of asialo-GM1+ graft-versus-host effector cells of donor origin

In previous studies we demonstrated that an induced asialo-GM1 positive (ASGM1+) cell of donor origin that exerts natural killer cell-like activity (NK activity+) plays a crucial role in the development of graft-versus-host (GVH)-associated tissue damage and severe immunosuppression. This study examined whether the ASGM1+ (NK activity+) GVH effector cells were activated by non-specific signals or whether these cells were triggered by specific alloantigens and displayed antigenic specificity. C57B1/6 (B6) donor mice were treated with either B6 x AF1 (B6AF1) lymphoid cells and anti-asialo GM1 antibodies (anti-ASGM1) to induce and eliminate specifically activated B6-anti-B6AF1 ASGM1+ (NK activity+) cells or with polyinosinic: polycytidylic acid (poly I:C), and anti-ASGM1 to eliminate non-specifically activated ASGM1+ (NK activity+) cells. Donor spleen and lymph node cells depleted of the specific allo-induced ASGM1+ NK reactive cells showed near normal numbers of L3T4+ and Lyt-2+ cells and retained T- and B-cell functions as measured by mitogen responses (to PHA, Con A and LPS), mixed lymphocyte responses (MLR) (to B6AF1) and the generation of cytotoxic T cells (CTL) (to B6AF1 blasts). Anti-ASGM1 treatment almost completely abrogated NK activity in all donor inocula. GVH reactions were induced by injecting treated donor cells into B6AF1, B6 x C3HejF1 (B6C3HF1) and B6 x SJLF1 (B6SJLF1) hybrids and monitored by splenomegaly, suppression of T-cell mitogen responses and the development of histopathological lesions in the thymus, liver and pancreas. Cells from donors depleted of non-specifically (poly I:C) induced ASGM1+ cells induced severe histological lesions, marked immunosuppression and splenomegaly in all three F1 hybrid combinations. When the donor cells were depleted of specifically induced (B6-anti-B6AF1) ASGM1+ cells and injected into the three F1 combinations they induced splenomegaly in all three but caused severe tissue injury and intense immunosuppression only in B6C3HF1 and B6SJLF1 mice and not in B6AF1 mice. Genetic analysis suggests that the H-2D (or a closely related) region of the H-2 complex plays an important role in the activation of the specific GVH effector cells. These results suggest that the cell(s) responsible for splenomegaly are different from the ones that cause severe GVH-associated tissue damage and immunosuppression although there may be cells and/or lymphokines common to both processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Predominant appearance of gamma/delta T lymphocytes in the liver of mice after birth

gamma/delta T lymphocytes residing in the liver of mice were systematically characterized with respect to their age-related variation, phenotype and V gene segment usage of gamma/delta T cell receptor (TcR). Previous human and murine studies have shown that a high proportion of gamma/delta T cells reside in the liver and that such liver gamma/delta T cells have lymphoblastic morphology and can spontaneously proliferate in vitro. In the present study, a predominant appearance of gamma/delta T cells (up to 23% among CD3+ cells) in the liver was confirmed in 4-week old mice of various strains. gamma/delta T cells in the liver preferentially co-expressed CD8 antigens, whereas the vast majority of gamma/delta T cells in the spleen lacked the CD8 antigens. The identification of gamma/delta T cells in various lymphoid and non-lymphoid organs also revealed the liver to be one of the organs where gamma/delta T cell are most abundant. The level of such liver gamma/delta T cells showed a clear age-related variation. In the fetal stage and just after birth, gamma/delta T cells were not detectable in the liver (less than 0.2%). However, a significantly higher percentage of gamma/delta T cells among both the total population of mononuclear cells and CD3+ cells was detected in the liver of young 2- to 8-week-old mice; this percentage subsequently declined. As the total number of liver mononuclear cells increased in aged mice, the absolute number of liver gamma/delta T cells also increased as a function of age. V gene segment usage analysis by the polymerase chain reaction method demonstrated that V gamma 1 or V gamma 2/V delta 6 were preferentially used by liver gamma/delta T cells. The age-related increase of gamma/delta T cells was more prominent in the liver of athymic nude mice, and such gamma/delta T cells highly co-expressed the CD8 antigens and also utilized the V gamma 1 or V gamma 2/V delta 6 for gamma/delta Tcr. The predominant appearance of unique gamma/delta T cells in the liver, which was inversely related to the existence of the thymus, indicates that these gamma/delta T cells may differentiate extrathymically in the liver.

The primary response of human gamma/delta + T cells to Mycobacterium tuberculosis is restricted to V gamma 9-bearing cells

We have previously reported that peripheral blood gamma/delta + T cells proliferate in high frequency (1 in 2-20) in response to heat-killed Mycobacterium tuberculosis (M.tb.). In the present study, the T cell receptor phenotype of mycobacteria-responsive human gamma/delta + T cells was analyzed in primary cultures with a set of monoclonal antibodies (mAbs) directed against V gamma 9, V delta 1, and V delta 2. When unseparated T cells were stimulated with M.tb., all proliferating gamma/delta + T cells expressed V gamma 9 (and V delta 2) after culture. Selective depletion of V gamma 9-bearing cells before culture completely abolished the proliferative response of all gamma/delta + cells (but did not inhibit reactivity of alpha/beta + T cells). In addition, when CD4- CD8- thymocytes were stimulated with M.tb., there was again selective outgrowth of V gamma 9+ cells. In this case, the starting responder population contained few (0.5-1.8%) V gamma 9+ and many (11.5-31.5%) V delta 1+ cells that did not coexpress V gamma 9. These V delta 1+ cells were not activated by M.tb. but could be readily stimulated by anti-V delta 1 mAb A13. Finally, a V gamma 9-specific mAb selectively suppressed the proliferative response of gamma/delta + T cells to M.tb. Taken together, our results demonstrate that, within gamma/delta + T cells, reactivity towards M.tb. is an exclusive property of V gamma 9+/V delta (2+)-bearing cells.

Rearrangement patterns of T-cell receptor genes in the spleen of athymic (nu/nu) young mice

Although the athymic nude mouse is grossly deficient in peripheral T cells, the number of lymphocytes bearing T-cell markers (L3T4, LyT2) and the alpha beta or gamma delta T-cell receptor (Tcr) increases steadily with age. The anatomical site(s) where these cells arise are unknown. Splenocytes from 3-5-week-old C57BL/6 (nu/nu) mice contain 2%-5% Pro-T cell progenitors identified with the Joro 37-5 and Joro 75 antibodies, but not mature T cells. To study Tcr gene rearrangement outside the thymus, we fused splenocytes from 3-5-week-old C57BL/6 nude mice with the T-cell lymphoma BW 100.129. Of 22 hybrids that grew stably in culture, four had Tcrd-VD1-D2-J1, two had Tcrd-VD2-J1, and seven had Tcrd-D1-D2 types of rearrangement. Eight hybrids had rearranged the Tcrg-2 gene cluster, but none had rearranged Tcrg-1, -3, or -4. None of the hybrids had rearranged the Tcrb gene cluster and 13 contained DJ rearrangements at the Igh locus. We conclude that the spleen is one of the extrathymic sites where T-cell progenitors can rearranged Tcrd and Tcrg genes. However, there was no evidence for Tcrb gene rearrangements in this organ. Furthermore, the analysis of this limited number of hybrids suggests that extrathymic Tcr gene rearrangements seem to be distinct and much less diverse than those found in the developing thymocytes.

Developmentally regulated fetal thymic and extrathymic T-cell receptor gamma delta gene expression

The gamma delta T-cell receptor (TCR) is the first TCR to be expressed in ontogeny in all vertebrates in which it has been examined thoroughly. Murine gamma delta cell-surface protein is detected by the fourteenth day of gestation. In this work, the activation of gamma delta RNA has been studied. Data indicate that the first TCR protein to appear in the thymus is encoded by gamma genes that are activated after cells colonize the thymus. However, the sequential appearance of different gamma delta TCR proteins during thymic ontogeny cannot be readily explained by differential temporal activation of V gamma genes in the thymus. There are distinct patterns of gamma and delta gene expression during fetal liver development and in the fetal gut (or tissue associated with it). Cells apparent in the liver of mice at birth express gamma delta cell-surface protein, but they disappear from the liver very soon afterward. One V gamma gene is rearranged and expressed prethymically. In addition, gamma gene expression is detectable in the livers of newborn athymic mice. Together, these observations indicate a thymic-independent pathway of activation of TCR genes.

The role of gamma delta T cells in the normal and disordered immune system

A small population of T cells does not express the conventional T cell receptor characterized by the alpha and beta polypeptide chains (TCR alpha beta) but instead, two polypeptides termed gamma and delta (TCR gamma delta). This alternative receptor is able to recognize antigen. It appears early in T cell ontogeny, but its role in the thymus prior to the availability of TCR alpha beta remains unclear. In selected sites such as skin or gut TCR gamma delta predominates in mice which might suggest a role of gamma delta T cells in the first line of defense against infection. gamma delta T cells secrete lymphokines and display cytotoxic activity. However, their activation requirements may differ from what is known for alpha beta T cells since MHC-nonrestricted and also CD4 and CD8 negative gamma delta T cells have been described. Preferential activation by mycobacterial antigens possibly indicates a special repertoire of the gamma delta T cells. In various diseases slightly increased numbers of gamma delta T cells were found, but these preliminary studies have not yet provided evidence for a major pathogenetic role of gamma delta T cells.

Polymorphisms and diversity of T-cell receptor-gamma proteins expressed in mouse spleen

Bulk populations of T-cell receptor (Tcr) gamma delta-expressing splenocytes from different inbred strains of mice were examined for the diversity of Tcr gamma delta proteins. Immunoprecipitations with anti-C gamma 1/2, anti-C gamma 4, and anti-V gamma 1 sera demonstrated that splenocytes from B10.BR, C57BL/6, and C57L strains of mice expressed the same array of Tcr gamma proteins, namely V gamma 1-C gamma 2, V gamma 1-C gamma 4, and V gamma 2-C gamma 1, although the Tcr gamma delta heterodimers observed for each of these strains were biochemically distinct. Examination of bulk splenic Tcr gamma delta heterodimers from several other inbred strains of mice demonstrated that each of the strains could be categorized into one of three basic phenotypes. For several reasons, the differences observed between the strains appeared to be solely dependent on polymorphisms of the Tcrg loci. First, F1 mice co-expressed both parental Tcr gamma delta phenotypes. Second, the distinguishing polymorphism between mice of phenotype 1 and phenotypes 2 or 3 was due to the presence of an N-linked glycosylation site within the Tcrg-Cl gene segment, previously described for BALB.B and C57BL/6 Tcrg-Cl genes. Finally, the V gamma 1-C gamma 4 polymorphism between mice of phenotype 3 and phenotypes 1 or 2 was due to differences in core protein size. Furthermore, the three defined Tcr gamma chains were expressed independently of the major histocompatibility complex (MHC) haplotype. Although no striking qualitative differences in Tcr gamma delta heterodimers were observed between strains (including those with autoimmune disorders), a quantitative difference in the relative amount of C gamma 4-encoded proteins was observed on Tcr gamma delta splenocytes from both newborn euthymic and adult athymic mice when compared to adult Tcr gamma delta splenocytes from euthymic mice. These results demonstrate that genetic polymorphisms exist among different mouse strains and suggest that selective developmental pressures may govern Tcr gamma delta expression.

Identification and characterization of rat T cell subpopulations expressing T cell receptors alpha/beta and gamma/delta

Peripheral lymphoid organs of the rat were investigated for the presence of lymphocytes that expressed the pan-T cell markers CD5 and OX-52 but not the T cell receptor (TcR) alpha/beta. Two such populations were identified: 2% to 4% of lymphocytes in adult spleen, lymph nodes and peripheral blood are CD5+ TcR alpha/beta- and express the OX-52 antigen at the same density as TcR alpha/beta+ T-cells. About 90% of these cells are CD8+. A second population is CD5-, CD8+ and OX-52low. Radioimmunoprecipitation from digitonin lysates of surface-labeled cells with an anti-CD3 antiserum showed that the CD5+, but not the CD5- population of TcR alpha/beta- cells expresses a CD3-associated disulfide-linked cell surface molecule of about 100 kDa apparent mol. mass. Upon reduction, one major band, migrating with 48 kDa was observed. A band of the same size was obtained with an anti-human delta chain peptide antiserum, indicating that the CD3-associated non-TcR alpha/beta molecule is the rat TcR gamma/delta. Functional assays showed that most, if not all natural killer (NK) cell activity is present in the CD5(-)-OX-52low population. Reactivity to foreign major histocompatibility complex (MHC) antigens in mixed lymphocyte reaction was exclusively found in TcR alpha/beta+ splenic T cells. It is concluded that rat gamma/delta T cells in the spleen do not contain a high frequency of cells with specificity for foreign MHC antigens. The seeding of the periphery with alpha/beta and the presumptive gamma/delta T cells was followed from birth. Most prominently in the spleen, alpha/beta T cells reached adult levels much later than gamma/delta T cells. Taken together, these findings demonstrate the expression of the TcR gamma/delta on a minor population of peripheral rat T cells with the predominant phenotype CD4-CD8+ that has no NK cell activity when freshly isolated and does not contain a high frequency of alloreactive cells.

Analysis of T cell receptor gamma chains from adult CD4- CD8- thymocytes

The role of T cell receptor (TcR) gamma genes in T cell development has not been determined. To extend our understanding of the repertoire of TcR gamma expression, we prepared a cDNA library from CD4-CD8- adult BALB/c thymocytes and cloned and sequenced 15 TcR gamma genes from this cDNA library. We found that two clones were transcripts of the unrearranged C gamma 2 gene and that three clones terminated in the J gamma 2 region. Nine of the remaining clones were V gamma 1.2 J gamma 2 C gamma 2 genes and five of these were in frame. Only one clone corresponded to C gamma 1 and resulted from an in-frame V gamma 2 J gamma 1 C gamma 1 join. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the gamma chain proteins from the surface of both BALB/c and C57BL/6 adult CD4-CD8- thymocytes did not detect the 32-kDa V gamma 1.2 C gamma 2 protein, but did detect the 35-kDa V gamma C gamma 1 protein. These results suggest that despite the abundance of full-length functional V gamma 1.2 C gamma 2 transcripts in the thymocyte subset, the protein product is not expressed on the cell surface as the predicted 32-kDa gamma protein. Finally, our analysis of the V-J joining of the gamma genes reveals both flexibility at the V-J junction and extensive N-region nucleotide addition that lead to diversity of the predicted protein sequence.

Monoclonal antibodies specific to native murine T-cell receptor gamma delta: analysis of gamma delta T cells during thymic ontogeny and in peripheral lymphoid organs

Three hamster monoclonal antibodies (mAbs), all recognizing different epitopes present on the native form of the murine T-cell antigen receptor (TCR) gamma delta subunits, have been generated. mAb 3A10 is specific to a pan-murine TCR gamma delta, recognizing a C delta constant region determinant. mAb 8D6 is specific to a subset of T cells expressing V gamma 4- and V delta 5-encoded gamma delta TCR, and mAb 5C10 is clonotypic. Using these and other mAbs directed against a variety of T-cell surface markers, we quantitated and characterized gamma delta T cells present in developing thymuses as well as in the conventional lymphatic organs by flow cytometry. These studies revealed that (i) many gamma delta thymocytes and peripheral T cells bear CD4 and/or CD8 molecules, (ii) T cells bearing both alpha beta and gamma delta TCRs are scarce, and (iii) thymocyte subsets bearing TCR gamma delta encoded by different combinations of V gamma and V delta gene segments appear in waves during ontogeny.

Diversity of gamma delta T-cell receptors on murine intestinal intra-epithelial lymphocytes

The search for the genes encoding the T-cell receptor (TCR) alpha- and beta-subunits revealed a third gene gamma which shares with the alpha- and beta-genes several properties including somatic rearrangement. This gene, together with a fourth rearranging gene delta, encodes a second type of T-cell receptor, TCR gamma delta. Although TCR gamma delta-bearing T cells constitute a relatively minor subpopulation in the thymus and in peripheral lymphoid organs, they are the major lymphocytes of epidermis (dendritic epidermal cells or DEC) and of intestinal epithelium (intestinal intraepithelial lymphocytes or IEL) in mice, suggesting that at least some gamma delta T cells are important in the surveillance of a variety of epithelia. It was recently reported, however, that the TCR gamma delta on DEC has essentially no structural diversity, implying that the putative ligand is monomorphic. As this finding, if generally applicable, poses severe restrictions on the origin of the ligand, we investigated the diversity of the TCR on the second major epithelium-associated gamma delta T cells, namely IEL from mice. We report here that by contrast with the DEC gamma delta, the IEL gamma delta TCR are structurally diverse.

Limited diversity of T-cell receptor gamma-chain expression of murine Thy-1+ dendritic epidermal cells revealed by V gamma 3-specific monoclonal antibody

To study the origin of and the degree of T-cell antigen receptor (TCR) diversity of Thy-1+ dendritic epidermal cells (Thy-1+ dECs) in mice, we have developed a monoclonal antibody (mAb 536) to the gamma delta TCR. mAb 536 binds to and stimulates interleukin 2 secretion from Thy-1+ dEC but not cells that express TCR composed of alpha and beta chains. mAb 536 precipitates CD3-associated gamma and delta chains from lysates of radioiodinated Thy-1+ dECs. Analysis of a panel of hybridomas that express gamma delta TCR indicated that mAb 536 defines an epitope of the variable region (V gamma 3) gene product. Flow cytometric analysis revealed that expression of V gamma 3 in the adult mouse is restricted to cells in the epidermis, where essentially all Thy-1+ cells are V gamma 3+. The majority of CD3+ cells in the 14-day fetal thymus also express V gamma 3. These results indicate that the T-cell complement in epidermis are cells that express gamma delta TCR and that the diversity of antigens recognized by the cells might be restricted by the use of a single V gamma gene segment. Finally, the data raise the intriguing possibility that Thy-1+ dECs may arise from precursors that are among the first to emerge from the developing thymus. This suggests that V gene usage during thymocyte development is highly regulated and has important consequences on the tissue localization and function of the emerging cells. As in other developing tissues, it appears that programmed and transient gene expression determines the fate of the emerging cells.

Development of a monoclonal antibody specific for the gamma chain of the T-cell antigen receptor using an open reading frame expression vector

To develop an anti-framework monoclonal antibody (mab) specific for the gamma (gamma)-chain of the T-cell antigen receptor (TCR), we expressed a part of the constant region of the gamma-chain (C gamma 2 gene segment) in E. coli using the pWR590 vector. This plasmid contains the E. coli lac promoter, operator, a truncated beta-galactosidase (beta-gal) gene (coding for the first 590 of the 1,007 amino acids of the beta-gal) and a polylinker region (at the 3' end of the beta-gal) containing nine restriction sites. These can be cleaved by any one of eight common restriction enzymes, permitting the introduction of the DNA fragment of interest. We employed the pT gamma 1 gamma-chain cDNA probe, which like the vast majority of the gamma-chain specific probes is aberrant and contains an in-frame stop codon at the junction of V and J regions. Computer analysis of the pT gamma 1 sequence revealed several MaeIII restriction sites that could result in a number of fragments. One of these fragments consisted of 245 base pairs (nucleotides 404-648) and contained most of the CI exon of the C gamma 2. Successful insertion of this fragment to the pWR590 vector was confirmed using restriction enzyme analysis. The C gamma insert was 12% of the construct. Expression of the pWR590-HpT gamma 1 recombinant plasmid in E. coli followed by SDS-PAGE analysis revealed a hybrid protein with a molecular weight of 85 kd which constituted at least 25% of the total E. coli insoluble protein. In contrast, cells transformed with the control pWR590 vector without insert expressed a 78 kd polypeptide chain. We developed several mabs against the pWR590-HpT gamma 1 hybrid protein by fusing spleen lymphocytes from BALB/c mice immunized with the pWR590-HpT gamma 1 protein, with cells of the NS1 mouse myeloma cell line. Screening of the mabs was carried out by ELISA against the pWR590-HpT gamma 1 hybrid protein and the control pWR590 beta-gal protein (beta-gal 590), derived by expressing in E. coli the pWR590 vector without gamma-chain insert. Two groups of mabs were obtained, those reacting with the pWR590-HpT gamma 1 hybrid protein only and those reacting with both the hybrid and the control beta-gal 590 proteins. The specificity of these mabs was further studied by Western blotting with similar results.(ABSTRACT TRUNCATED AT 400 WORDS)

Dendritic epidermal T cells: activation requirements and phenotypic characterization of proliferating cells

Dendritic epidermal T cells (DETC) are CD45+, Thy-1+, CD5-, CD8-, CD4- murine lymphocytes that express surface-bound CD3 antigens associated with T cell receptor gamma/delta heterodimers. Using epidermal cells greatly enriched for DETC and depleted of Langerhans cells, we found that DETC have growth requirements quite different from those of accessory cell-depleted lymph node and splenic T cells. Although the latter cells strongly proliferate in response to phorbol myristate acetate (PMA) + ionomycin, DETC, when exposed to interleukin-1 (IL-1), interleukin-3 (IL-3), concanavalin A (ConA), PMA, and ionomycin used either alone or in combination, do not exhibit significant mitotic activity. Recombinant interleukin 2 (rIL-2), albeit ineffective by itself, leads to vigorous proliferation of DETC when used with either ConA or PMA + ionomycin + IL-1. In contrast, the combination of PMA and recombinant interleukin-4 (rIL-4), which triggers growth of lymph node T cells, does not induce proliferation of DETC. Although a portion of proliferating DETC expressed CD8 antigens, essentially none bore detectable amounts of surface-bound CD4 or CD5 antigens, or both. Continuing stimulation of primary DETC cultures with lectin/lymphokine-rich media results in the propagation of cells with the essential phenotypic features of resident DETC.

TCR3: a third T-cell receptor in the chicken

Avian homologues of mammalian gamma delta and alpha beta T-cell antigen receptors, TCR1 and TCR2, have been identified with monoclonal antibodies. These TCR isotypes are associated with the avian CD3 proteins on the T-cell surface. During chick development, T-cell subpopulations bearing CD3/TCR1 or CD3/TCR2 receptor complexes are generated sequentially in the thymus and seeded to the periphery in the same order. In this study, we used two-color immunofluorescence to identify the subsequent development of a third subpopulation of T cells, provisionally named TCR3. These CD3+ cells, which expressed neither TCR1 nor TCR2, were first detected in the blood 1 week after hatching and increased numerically as a function of age to account for approximately 15% of the circulating T-cell pool in adults. Most (greater than 80%) of the TCR3 cells expressed the CD4 accessory molecule. The relative incidence of the TCR3 subpopulation increased dramatically as a consequence of embryonic treatment with anti-TCR2 antibody and thymectomy after hatching. Two disulfide-linked polypeptides, of Mr 48,000 and 40,000, were associated with the CD3 complex on the TCR3 cells. Examination of the TCR protein backbones and peptide mapping of the TCR chains after partial proteolysis indicated that the TCR3 heterodimer differs from both TCR1 and TCR2. These results suggest the existence of a third class of T-cell receptors in birds.

A monoclonal antibody to a constant determinant of the rat T cell antigen receptor that induces T cell activation. Differential reactivity with subsets of immature and mature T lymphocytes

mAb R73 detects a T cell-specific surface molecule consisting of two disulfide-linked subunits of 40 and 46 kD, respectively, on 97% of peripheral rat T cells, as defined by the OX-52 marker. Of the few OX-52+ R73- cells, none are CD4+ but many express the CD8 antigen known to be present on rat NK cells. mAb R73 is mitogenic for unseparated spleen cells and for purified T cells. In the absence of non-T "accessory cells", stimulation by R73 requires artificial crosslinking of the mAb and is largely dependent on exogenous IL-2. Overnight incubation of purified T cells with crosslinked R73 mAb induces blastoid transformation, IL-2-R expression, and modulation of the R73 antigen. In the rat thymus, mature medullary cells express the R73 determinant at the same level as peripheral T cells, whereas 94% of CD4-CD8- thymocytes are R73-. The major CD4+8+ thymocyte population contains 25% R73- and 70% R73low cells. Thymocytes of the CD4-CD8+OX-44- subpopulation that are the direct precursors of CD4+CD8+ cells display a continuum of R73 antigen density from undetectable to very low levels. We conclude that R73 is most likely directed at a constant determinant of the rat alpha/beta heterodimeric TCR and suggest that CD8+ immature thymocytes are the first cells in the T cell differentiation pathway to express this molecule at their surface.

Different gamma delta T-cell receptors are expressed on thymocytes at different stages of development

We have analyzed the structural diversity of the murine gamma delta T-cell receptor (TCR) heterodimer expressed on CD4- CD8- thymocyte populations and on TCR gamma delta-expressing hybridomas derived from thymocytes of fetal, newborn, and adult mice. We found that CD4- CD8- thymocytes derived from mice of different pre- and postnatal age preferentially express a gamma delta TCR encoded by different subsets of gamma and delta gene segments. This age-dependent differential expression of gamma delta TCR on thymocytes seems to be accomplished in part by a specific control of rearranged gamma genes operating at the level of transcription and/or RNA stability. We discuss the implications of these findings with respect to the recognition roles of the gamma delta TCR.

Detection and characterization of functional T cells in mice with severe combined immune deficiency

CD3+ alloresponsive T cell clones were derived from mice with severe combined immune deficiency (scid mice). T cell receptor beta and gamma gene rearrangements were analyzed to obtain insight into the nature and origin of these clones. We hypothesized that developing scid lymphocytes with an active, impaired recombinase system might generate functional lymphocytes by rare productive rearrangements at two critical antigen receptor loci. One alloresponsive clone showed evidence of both normally rearranged T cell receptor genes and genes with abnormal J region-associated deletions, supporting this hypothesis. Four additional alloresponsive clones, however, showed only conventional gene rearrangements. These data leave open the possibility that the recombinase activity, believed defective in scid mice, may be normalized in rare early B and T lymphoid cells or their precursors, to give rise to functional lymphocytes.

Molecular analysis of T cell receptor gamma gene expression in allo-activated splenic T cells of adult mice

Northern analysis, hybridization in situ and cDNA sequence analysis have been used to demonstrate that the induction of T cell gamma-gene expression is a general occurrence when primary splenic T cells of adult mice are cultured in short-term mixed lymphocyte reactions (MLR). Splenic T cells from nine strains of mice examined in eleven different MLR all showed significant induction of gamma-RNA, even when the primary T cell response was to only a three amino acid mismatch in a major histocompatibility complex class I antigen. In MLR examined in detail, the expression is highly enriched for in CD3+ "double-negative" T cells (lacking both CD4 and CD8 expression). A cDNA sequence analysis, constituting the first such analysis of any size of gamma-gene transcripts from circulating, peripheral cells of adult mice, revealed transcription to be frequently of productively rearranged genes. These genes display extensive junctional diversity.

Intestinal intraepithelial lymphocytes are a distinct set of gamma delta T cells

Lymphocytes are most reliably subdivided on the basis of their receptors for antigen at the cell surface. Three subtypes of lymphocytes are well defined: B cells that bear surface immunoglobulin and make antibody, CD4+T cells with CD3 alpha beta receptors specific for antigen associated with class II major histocompatibility complex molecules, and CD8+T cells with CD3 alpha beta receptors specific for antigen associated with class I MHC molecules. These T cells are responsible for known forms of cell-mediated immunity. The discovery of a third rearranging T-cell specific gene called gamma (refs 1 and 2) has revealed the presence of a new class of T cells bearing a new receptor type, CD3 gamma delta (refs 3-7). To date, neither the function nor the specificity of cells bearing this receptor has been determined. Because gamma delta T cells are the main lymphocyte of epidermis, it was proposed that such cells could be important in surveillance of all epithelia. We have isolated intraepithelial lymphocytes from murine small intestine, and shown that they predominantly or exclusively express CD3 gamma delta receptors. Unlike the epidermal lymphocytes, these cells also express CD8, and they use a different V lambda gene to form their receptor. This strongly suggests that gamma delta T cells home in a very specific manner to epithelia, where they presumably mediate their function.

Early expression of a T-cell receptor beta-chain transgene suppresses rearrangement of the V gamma 4 gene segment

beta transgenic mice have a T-cell receptor beta-chain gene that is prematurely expressed on the surface of CD4- CD8- thymocytes and paired with an uncharacterized non-T-cell receptor alpha-chain polypeptide. The rearrangement of the T-cell receptor variable region gamma chain gene segment V gamma 4, a component of the gamma-chain gene that is rearranged and expressed preferentially on thymocytes of normal adult mice, is severely repressed in beta transgenic mice. Consequently no gamma delta T-cell receptor heterodimers are detectable on the surface of adult thymocytes or splenic T cells. These results indicate that cells expressing alpha beta or gamma (V gamma 4)-delta TCRs originate from a common precursor in which the first productive rearrangement of either the beta or gamma locus determines the further differentiation pathway into either alpha beta or gamma delta T cells. The repression of V gamma 4 rearrangement by a preexisting beta-chain gene may be indicative of one of several mechanisms which ensure that gamma delta and alpha beta receptors do not as a rule appear on the surface of the same cell.

Age-associated increase in the expression of T cell antigen receptor gamma chain genes in mice

T cell function generally declines with age. To determine the underlying cause of the age-related decline, we compared the expression levels of T cell antigen receptor genes encoding gamma, beta and alpha chains in the lymphoid tissues of young (8 wk old) vs. aged (40 wk old) mice. An age-associated increase in gamma chain gene transcripts was evident in the thymocytes, spleen cells and mesenteric lymph node cells. Aged mice had a relatively high proportion of CD3+CD4-CD8- cells but a reduced level of CD3+CD4-CD8+ cells in the lymphoid tissues, as compared with young counterparts. The allo-reactivity in the lymphoid cells, as assessed by mixed lymphocyte reaction (MLR) responses, decreased with advancing age. On the contrary, increased levels of syngeneic MLR and spontaneous cytolytic activity were noted in the lymphoid cells of aged mice, as compared with findings in their young counterparts. A remarkable increase in the number of CD3+CD4-CD8- cells and level of the gamma chain gene messages was also detected in the responder cells of day 4 syngeneic MLR culture from aged mice. An increase in the number of T cells bearing gamma chain may be related to the alterations in immunological functions in aged mice.

Functional T cell receptor delta chain gene messages in athymic nude mice

The rearrangement and expression of T cell antigen receptor (TcR) delta chain genes were investigated in congenitally athymic nude mice. The lymphoid cells derived from nude mice showed evidence of rearranged delta chain genes and a relatively high level of delta chain gene messages. Nucleotide sequence analysis revealed that nude mice contained an in-frame delta chain transcript, composed of V delta 5-D delta 1-D delta 2-J delta 1-C delta genes in the spleen. We have previously described functionally rearranged TcR gamma chain genes in the spleen of nude mice. Taken together, T cell precursors appear to proliferate and differentiate along the extrathymic pathway into TcR gamma/delta-bearing T cells in nude mice.

Mapping genomic organization by field inversion and two-dimensional gel electrophoresis: application to the murine T-cell receptor gamma gene family

A new two-dimensional gel electrophoresis technique has been developed for the mapping of multigene families. Resolution in the first dimension is based on the generation of large size DNA fragments by infrequently-cutting restriction enzymes, and separation of these fragments by field inversion gel (FIG) electrophoresis. A second restriction enzyme digestion is then carried out with the separated DNA fragments in the agarose gel. Standard gel electrophoresis in the second dimension allows one to estimate the number of hybridizing genes contained in each large DNA fragment. We have also developed a novel method to increase the separation, resolution and hybridization signal in the second dimension by condensing the bands from the first dimension into spots. As an example, we have applied these techniques to determine the organization of the murine T-cell receptor gamma locus. The murine gamma gene family was found to be contained on two DNA fragments encompassing 195 kilobases of DNA. The two-dimensional gel electrophoresis method is particularly useful in the analysis of the organization of multigenic families where single copy probes are not readily available, and should extend the potential usefulness of field inversion gel electrophoresis in gene mapping.

Analysis of CD3 and antigen receptor expression on T cell subpopulations of aged athymic mice

The expression of the T cell antigen receptor on subpopulations of extrathymically generated T cells from athymic mice was investigated and compared to antigen receptor expression in normal mice. To this end, spleen and lymph node cells from 18 individual athymic BALB/c nu/nu mice between 6 and 12 months of age and from normal controls were enriched for T cells by nylon wool filtration. Expression of the following cell surface markers was analyzed by two-color flow cytometry: Thy-1, CD4, CD8, V beta 8 and CD3. The distribution of subpopulations as defined by these markers varied much more among athymic than among normal mice. Some recurrent patterns did, however, occur that may be characteristic of the extrathymic pathway of T cell differentiation in nu/nu mice. Among Thy-1.2+ cells, CD8+ cells predominated over CD4+ cells. No CD4+8+ "double positive" cells were found, but CD4-8- "double negative" cell constituted 16% on average. All nu/nu nylon wool-nonadherent cells expressing Thy-1 at a normal level also expressed CD3, whereas Thy-1low and Thy-1- cells were CD3-. The fraction of V beta 8 T cells among the CD4+ and CD8+ subsets was near to normal in the majority of these animals. Most interestingly, the density of V beta 8 and CD3 expression was lower in athymic than in euthymic animals. This level of T cell antigen receptor expression was, however, higher than on immature CD4+8+ thymocytes. A fraction of the nude T cells presently characterized responded with proliferation to both anti-T cell receptor V beta 8 monoclonal antibody and to concanavalin A. Despite their apparently normal phenotype (with the exception of reduced T cell receptor expression), this response was, however, 4 to 10 times smaller than that of normal control cells. The presently described Thy-1+ T cell receptor intermediate cells may either be a(n) aberrant lineage(s) only generated extrathymically, or represent the accumulation of an immature intermediate stage of normal (i.e. thymic) T cell differentiation.