Hybridomas expressing gammadelta T-cell receptors respond to cardiolipin and beta2-glycoprotein 1 (apolipoprotein H).

Hybridomas expressing murine gammadelta T-cell receptors were found to produce cytokines in response to cardiolipin (CL) and structurally related anionic phospholipids. This response required serum at concentrations related to the amount of CL in cultures. The purified serum factor, beta2-glycoprotein 1 (beta2-GP1) (apolipoprotein H), supported the CL response alone, whereas several other serum proteins and ovalbumin did not. beta2-GP1 is known to form complexes with anionic phospholipids, particularly CL, which are often recognized by pathological autoantibodies. We speculate that gammadelta T cells also recognize such complexes and that the hybridoma response reported here reflects this specificity.

gammadelta T cells as regulators of airway hyperresponsiveness.

Airway responsiveness (AR) is determined by complex mechanisms reflecting lung responses to airborne stimuli. Murine studies have identified a number of potential factors modulating AR and thus have contributed to the current understanding of these mechanisms. In allergic inflammation, immune cells, in particular alphabeta T cells, have emerged as important contributors to increased AR. We have found that in contrast to alphabeta T cells, gammadelta T cells can have a negative regulatory effect on AR. Here, we review the current studies on gammadelta T cells in allergic inflammation and discuss their role in modulating AR. We propose that gammadelta T cells exhibit different immune properties depending on the type of stimulus and inflammation. These differential immune properties appear to be associated with specific gammadelta T cell subsets, which control AR to airborne stimuli. In particular, our recent data indicate that the Vgamma4(+) T cell subset acts as an important negative regulator of AR and contributes to maintaining normal lung function in mice.

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.

Cytokine production by Vgamma(+)-T-cell subsets is an important factor determining CD4(+)-Th-cell phenotype and susceptibility of BALB/c mice to coxsackievirus B3-induced myocarditis.

Two coxsackievirus B3 (CVB3) variants (H3 and H310A1) differ by a single amino acid mutation in the VP2 capsid protein. H3 induces severe myocarditis in BALB/c mice, but H310A1 is amyocarditic. Infection with H3, but not H310A1, preferentially activates Vgamma4 Vdelta4 cells, which are strongly positive for gamma interferon (IFN-gamma), whereas Vgamma1 Vdelta4 cells are increased in both H3 and H310A1 virus-infected animals. Depletion of Vgamma1(+) cells using monoclonal anti-Vgamma1 antibody enhanced myocarditis and CD4(+)-, IFN-gamma(+)-cell responses in both H3- and H310A1-infected mice yet decreased the CD4(+)-, IL-4(+)-cell response. Depleting Vgamma4(+) cells suppressed myocarditis and reduced CD4(+) IFN-gamma(+) cells but increased CD4(+) IL-4(+) T cells. The role of cytokine production by Vgamma1(+) and Vgamma4(+) T cells was investigated by adoptively transferring these cells isolated from H3-infected BALB/c Stat4 knockout (Stat4ko) (defective in IFN-gamma expression) or BALB/c Stat6ko (defective in IL-4 expression) mice into H3 virus-infected wild-type BALB/c recipients. Vgamma4 and Vgamma1(+) T cells from Stat4ko mice expressed IL-4 but no or minimal IFN-gamma, whereas these cell populations derived from Stat6ko mice expressed IFN-gamma but no IL-4. Stat4ko Vgamma1(+) cells (IL-4(+)) suppress myocarditis. Stat6ko Vgamma1(+) cells (IFN-gamma(+)) were not inhibitory. Stat6ko Vgamma4(+) cells (IFN-gamma(+)) significantly enhanced myocarditis. Stat4ko Vgamma4(+) cells (IL-4(+)) neither inhibited nor enhanced disease. These results show that distinct gammadelta-T-cell subsets control myocarditis susceptibility and bias the CD4(+)-Th-cell response. The cytokines produced by the Vgamma subpopulation have a significant influence on the CD4(+)-Th-cell phenotype.

Depletion of a gamma delta T cell subset can increase host resistance to a bacterial infection.

Gammadelta T lymphocytes have been shown to regulate immune responses in diverse experimental systems. Because distinct gammadelta T cell subsets, as defined by the usage of certain TCR V genes, preferentially respond in various diseases and disease models, we have hypothesized that the various gammadelta T cell subsets carry out different functions. To test this, we compared one particular gammadelta T cell subset, the Vgamma1(+) subset, which represents a major gammadelta T cell type in the lymphoid organs and blood of mice, to other subsets and to gammadelta T cells as a whole. Using Listeria monocytogenes infection as an infectious disease model, we found that bacterial containment improves in mice depleted of Vgamma1(+) gammadelta T cells, albeit mice lacking all gammadelta T cells are instead impaired in their ability to control Listeria expansion. Our findings indicate that Vgamma1(+) gammadelta T cells reduce the ability of the innate immune system to destroy Listeria, even though other gammadelta T cells as a whole promote clearance of this pathogen.

V gamma 1+ T cells suppress and V gamma 4+ T cells promote susceptibility to coxsackievirus B3-induced myocarditis in mice.

Coxsackievirus B3 infections of C57BL/6 mice, which express the MHC class II IA but not IE Ag, results in virus replication in the heart but minimal myocarditis. In contrast, Bl.Tg.Ealpha mice, which are C57BL/6 mice transgenically induced to express IE Ag, develop significant myocarditis upon Coxsackievirus B3 infection. Despite this difference in inflammatory damage, cardiac virus titers are similar between C57BL/6 and Bl.Tg.Ealpha mice. Removing gammadelta T cells from either strain by genetic manipulation (gammadelta knockout(ko)) changes the disease phenotype. C57BL/6 gammadelta ko mice show increased myocarditis. In contrast, Bl.Tg.Ealpha gammadelta ko mice show decreased cardiac inflammation. Flow cytometry revealed a difference in the gammadelta cell subsets in the two strains, with Vgamma1 dominating in C57BL/6 mice, and Vgamma4 predominating Bl.Tg.Ealpha mice. This suggests that these two Vgamma-defined subsets might have different functions. To test this possibility, we used mAb injection to deplete each subset. Mice depleted of Vgamma1 cells showed enhanced myocarditis, whereas those depleted of Vgamma4 cells suppressed myocarditis. Adoptively transfusing enriched Vgamma4(+) cells to the C57BL/6 and Bl.Tg. Ealpha gammadelta ko strains confirmed that the Vgamma4 subset promoted myocarditis. Th subset analysis suggests that Vgamma1(+) cells biased the CD4(+) T cells to a dominant Th2 cell response, whereas Vgamma4(+) cells biased CD4(+) T cells toward a dominant Th1 cell response.

Response of murine gamma delta T cells to the synthetic polypeptide poly-Glu50Tyr50.

Random heterocopolymers of glutamic acid and tyrosine (pEY) evoke strong, genetically controlled immune responses in certain mouse strains. We found that pE50Y50 also stimulated polyclonal proliferation of normal gamma delta, but not alpha beta, T cells. Proliferation of gamma delta T cells did not require prior immunization with this Ag nor the presence of alpha beta T cells, but was enhanced by IL-2. The gamma delta T cell response proceeded in the absence of accessory cells, MHC class II, beta 2-microglobulin, or TAP-1, suggesting that Ag presentation by MHC class I/II molecules and peptide processing are not required. Among normal splenocytes, as with gamma delta T cell hybridomas, the response was strongest with V gamma 1+ gamma delta T cells, and in comparison with related polypeptides, pE50Y50 provided the strongest stimulus for these cells. TCR gene transfer into a TCR-deficient alpha beta T cell showed that besides the TCR, no other components unique to gamma delta T cells are needed. Furthermore, interactions between only the T cells and pE50Y50 were sufficient to bring about the response. Thus, pE50Y50 elicited a response distinct from those of T cells to processed/presented peptides or superantigens, consistent with a mechanism of Ig-like ligand recognition of gamma delta T cells. Direct stimulation by ligands resembling pE50Y50 may thus selectively evoke contributions of gamma delta T cells to the host response.

Role of gammadelta T cells in protecting normal airway function.

Since their discovery 15 years ago, the role of gammadelta T cells has remained somewhat elusive. Responses of gammadelta T cells have been found in numerous infectious and non-infectious diseases. New evidence points to gammadelta T cells' functioning in the airways to maintain normal airway responsiveness or tone. In the lung, distinct subsets of gammadelta T cell subsets seem to have specific roles, one subset promoting allergic inflammation, the other serving a protective role.

gamma delta+ T cells regulate major histocompatibility complex class II(IA and IE)-dependent susceptibility to coxsackievirus B3-induced autoimmune myocarditis.

Coxsackievirus B3 (CVB3) infection induces myocardial inflammation and myocyte necrosis in some, but not all, strains of mice. C57BL/6 mice, which inherently lack major histocompatibility complex (MHC) class II IE antigen, develop minimal cardiac lesions despite high levels of virus in the heart. The present experiments evaluate the relative roles of class II IA and IE expression on myocarditis susceptibility in four transgenic C57BL/6 mouse strains differing in MHC class II antigen expression. Animals lacking MHC class II IE antigen (C57BL/6 [IA+ IE-] and ABo [IA- IE-]) developed minimal cardiac lesions subsequent to infection despite high concentrations of virus in the heart. In contrast, strains expressing IE (ABo Ealpha [IA- IE+] and Bl.Tg.Ealpha [IA+ IE+]) had substantial cardiac injury. Myocarditis susceptibility correlated to a Th1 (gamma interferon-positive) cell response in the spleen, while disease resistance correlated to a preferential Th2 (interleukin-4-positive) phenotype. Vgamma/Vdelta analysis indicates that distinct subpopulations of gamma delta+ T cells are activated after CVB3 infection of C57BL/6 and Bl.Tg.Ealpha mice. Depletion of gamma delta+ T cells abrogated myocarditis susceptibility in IE+ animals and resulted in a Th1-->Th2 phenotype shift. These studies indicate that the MHC class II antigen haplotype controls myocarditis susceptibility, that this control is most likely mediated through the type of gamma delta T cells activated during CVB3 infection, and finally that different subpopulations of gamma delta+ T cells may either promote or inhibit Th1 cell responses.

Inflammation alone evokes the response of a TCR-invariant mouse gamma delta T cell subset.

Whether gamma delta 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 V gamma 6/V delta 1 gamma delta T cells preferentially increase among the gamma delta 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 gamma delta T cells were still plentiful among the infiltrating T lymphocytes, being 9- to 10-fold more prevalent than in spleen, and that V gamma 6/V delta 1+ cells again represented the predominant gamma delta T cell type. This finding shows that the response of the V gamma 6/V delta 1+ subset does not, in fact, depend upon the presence of bacteria or bacterial products. The stimulus triggering the response of the V gamma 6/V delta 1 gamma delta 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.

Evidence that the same gamma delta T cells respond during infection-induced and autoimmune inflammation.

Inflammatory responses are induced in both testes of a mouse following injection of Listeria monocytogenes into one testis. Although the uninjected testis contains no detectable bacteria, it undergoes an autoimmune attack. Normally, the testis lacks lymphocytes, but in the infected and autoimmune state, both gamma delta and alpha beta T cells are found as infiltrates. Here, we have examined the repertoire of the infiltrating gamma delta T cells, using two different methods, and found a high frequency of V gamma 6/V delta 1 gamma delta T cells in both infected and autoimmune testes. All of these expressed the invariant V gamma 6/V delta 1 TCR previously reported. However, secondary gamma and delta transcripts present within V gamma 6/V delta 1 hybridomas indicated nonclonality. Interestingly, some of these secondary transcripts were derived from gamma gene rearrangements not previously found in this gamma delta T cell subset, implying a difference in its origin. The increase in V gamma 6/V delta 1 cells observed here in both infected and autoimmune testes, together with our previous finding of a preferential response by the same subset in Listeria-infected liver, indicates that their response is triggered by the inflammation rather than by the infectious agent or because they are already resident in the tissue. We and others have previously reported that the presence of gamma delta T cells during certain inflammatory conditions correlates with less host tissue damage. This result, together with the evidence presented here, further implies that a response by the V gamma 6/V delta 1 subset in some way exerts a controlling influence on the host inflammatory response.

Bias in the gamma delta T cell response to Listeria monocytogenes. V delta 6.3+ cells are a major component of the gamma delta T cell response to Listeria monocytogenes.

Despite extensive research, the role that gamma delta T cells play in the immune response to infectious disease has yet to be established. Here we report the generation of a mAb specific for the V delta 6.3 TCR and investigate the gamma delta+ and V delta 6.3+ T cell responses to the intracellular bacterium Listeria monocytogenes in BALB/c mice. By infecting animals with various doses of Listeria and analyzing the components of the cellular immune response at the two primary sites of infection, the liver and spleen, we have shown that the kinetics, composition, and magnitude of the gamma delta and V delta 6.3 T cell responses are dependent upon the injected dose of bacteria and the organ in which the infection is established. At low doses of infection, the gamma delta T cell response occurs late in the disease course, while at high doses, the response is earlier and of greater magnitude, particularly in the liver. At all infectious doses and in both tissues, the V delta 6.3+ population predominates and together with V delta 4+ cells composes the bulk of the gamma delta T cell response. Changes in the morphology of gamma delta+ and V delta 6.3+ cells at the site of infection are consistent with cellular activation and suggest that these cells are active participants in the Listeria-induced immune response. The results of our study suggest that many features of the gamma delta T cell response to Listeria are dose and tissue related.

Response of a gamma delta+ T cell receptor invariant subset during bacterial infection.

Murine gamma delta T cells can be divided into subsets based on the TCR gamma-chains they express. Most of these subsets have variable TCR junctions, but two, both associated with epithelia, express invariant TCRs. The absence of receptor variability in these cells implies uniformity of their ligands. This was previously taken as evidence to suggest that gamma delta T cells recognize host-derived, stress-induced ligands. We now demonstrate, for the first time, the response of a gamma delta TCR invariant subset during bacterial infection, a potential cause of stress. After infection with Listeria monocytogenes, absolute numbers of all T cells in the liver, including alpha beta and gamma delta T cell subsets, increased markedly. However, responses of a gamma delta T cell subset varied. We noted a decrease in the relative frequency of V delta 6.3+ cells, which are, for the most part, included in the V gamma 1+ subset. In contrast, cells bearing the invariant V gamma 6/V delta 1 TCR increased substantially in proportion to other gamma delta T cells, as determined by PCR analysis of liver T cell RNA and by comparing liver gamma delta T cell hybridomas made from normal mice to those from mice infected with Listeria. V gamma 6/V delta 1+ cells have been previously reported as a TCR invariant intraepithelial subset in the female reproductive tract and tongue. We show here that V gamma 6/V delta 1+ cells reactive in Listeria-infected liver are polyclonally derived, but still bear TCR chains with invariant junctional sequences, identical with those of the female reproductive tract. Although the Ag that stimulates these cells is unknown, our results indicate that only diverse, but also invariant, gamma delta T cell subsets can become involved in the host response to a bacterial infection.

Phenotypic and functional properties of murine gamma delta T cell clones derived from malaria immunized, alpha beta T cell-deficient mice.

Six murine T cell clones expressing gamma delta TCR were generated from malaria immunized, alpha beta T cell-deficient mice. Phenotypic characterization of these clones has revealed that, in contrast to conventional alpha beta T cells, there is a considerable degree of heterogeneity among these gamma delta clones with regard to their surface markers and their lymphokine profile. One clone was found to display significant anti-parasite activity in vivo upon adoptive transfer. We attempted to determine whether the protective clone differs in one or more key characteristics from the non-protective clones. Although no obvious pattern peculiar to the protective gamma delta clone was observed, it appears that more than one parameter may, in combination, define a distinct protective phenotype, and thus explain the functional difference between the protective and non-protective gamma delta clones.

Improvement in the organ donation rate at a large urban trauma center.

OBJECTIVE: To implement and then determine the efficacy of a "hospital development" (HD) plan designed to increase organ donation rates at an urban trauma center. DESIGN/SETTING: Retrospective reviews of all deaths at an urban, level I trauma center for 1991 to 1994. SUBJECTS: Potential organ donors were identified by standardized criteria, and the reasons why potential donors did not become actual organ donors ("nonproductive donors") were categorized. Actual donors were defined as individuals in whom one transplantable organ was recovered. Results also were expressed as percentages of potential donors for each year. Changes in actual donor numbers and in nonproductive donor categories were compared for the "pre-HD" (1991-1992) and "post-HD" (1993-1994) periods. INTERVENTION: The HD plan had six components: identification of key contact individuals, development and modification of relevant hospital policies, improvement in procurement agency visibility in hospital units, education of hospital staff regarding organ donation, institution of early on-site donor evaluations, and provision of feedback to hospital staff about the disposition of potential organ donors. RESULTS: Institution of the HD plan was associated with a highly significantly increase in actual donors for the post-HD period as compared with the pre-HD period (P < .001), and pre-HD and post-HD donor rates were 26.1% and 49.5%, respectively. This increase was due primarily to a marked improvement in hospital staff identification and referral of potential donors (P < .001). CONCLUSIONS: A coordinated plan incorporating continuing staff education, organ donation policy refinement, and increased visibility and availability of organ procurement agency personnel can substantially increase organ donation at an urban trauma center.

Murine epidermal V gamma 5/V delta 1-T-cell receptor+ T cells respond to B-cell lines and lipopolysaccharides.

The V gamma 5/V delta 1(+)-T-cell receptor (TCR)-bearing T-cell clone, 2CBET-3, was generated from C57BL/6 mice. Upon stimulation, 2CBET-3 cells produce interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-alpha, but not IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, macrophage colony-stimulating factor, or interferon-gamma. These cells were evaluated for their ability to be stimulated by a variety of murine cell lines, including fibroblasts, trophoblasts, melanoma cells, embryonic carcinomas, B-cell lymphomas, mastocytoma cells, and keratinocytes. The human B-lymphoma cell line, Daudi, also was included in these studies. We found that 2CBET-3 cells produced cytokines up to several hundredfold above the control levels in response to the B-cell lines, Daudi, and A20/2J, but not to the B-cell line 439.4.2. After fixation with glutaraldehyde, Daudi and A20/2J continued to stimulate this gamma delta T-cell line. 2CBET-3 cells also responded to the keratinocyte line PAM212, but not to another, XB-2. When lipopolysaccharides (LPS) from Escherichia coli or S. typhimurium were added to 2CBET-3 cells in the presence of A20/2J cells, 2CBET-3 cells responded with increased cytokine production compared with the cytokine production in the presence of A20/2J cells alone. 2CBET-3 cells by themselves did not respond to LPS alone or to supernatants from A20/2J cells incubated with LPS. Unlike 2CBET-3, the epidermal T-cell hybridoma 70BET-49, expressing a V gamma 5/V delta 1-TCR identical to that of 2CBET-3, did not respond to A20/2J cells in the presence or absence of LPS, suggesting a requirement for molecules other than the TCR for V gamma 5/V delta 1-TCR+ T-cell stimulation by the B-cell lines and by LPS. This unique reactivity of gamma delta-TCR+ cells is different from that of alpha beta-TCR+ cells and may reflect a functional specialization of gamma delta-TCR+ cells in the response to bacterial infections.

Response of a murine epidermal V gamma 1/V delta 6-TCR+ hybridoma to heat shock protein HSP-60.

In the epidermis, the major population of T lymphocytes expresses a T-cell receptor (TCR) with V gamma 5 and V delta 1 variable regions, which is unique to this tissue. Roberts et al and Ezquerra et al, also describe a minor population of gamma delta-TCR+ cells in the epidermis that expresses a V gamma 1/V delta 6 TCR. These cells are different from other epidermal T cells in that they "spontaneously" produce cytokines, a result thought to be due to autoreactivity. Over the past 5 years, our laboratory has produced V gamma 1/V delta 6+ T-cell hybridomas from many tissue sources. These spontaneously produce cytokines but also are activated by heat shock protein (HSP-60)-derived peptides. Ezquerra et al report that none of their V gamma 1/V delta 6+ epidermal T-cell lines derived from C3H/HeN mice respond to HSP-60. Of the 99 gamma delta-TCR+ hybridomas we have produced from epidermal T cells of C57BL/6 mice, only one expressed the V gamma 1/V delta 6 TCR. This hybridoma, 70BET-2.12, not only spontaneously produces cytokines, but, unlike the V gamma 1/V delta 6-TCR+ epidermal T cells of Ezquerra et al, it also responds to the whole HSP-60 protein and a 17-mer HSP-60 peptide from M. leprae, producing increased levels of interleukin-2 of up to approximately ten-fold above the spontaneous level. This shows that V gamma 1/V delta 6-TCR+ epidermal T cells can respond to HSP-60. To confirm that 70BET-2.12 expresses TCR genes similar to those of cells that have HSP-60 reactivity, V gamma 1-C gamma 4 and V delta 6-C delta cDNA were produced from RNA isolated from this hybridoma, amplified by the polymerase chain reaction, and sequenced. The gamma and delta TCR gene sequences were similar but not identical to previously published sequences of HSP-60-reactive cells from lymphoid and other organs. No explanation can be found for the discrepancy between our findings and those of others at the level of TCR expression such that other strain-specific factors might be responsible for HSP-60 reactivity.

Allelic differences in TCR gamma-chains alter gamma delta T cell antigen reactivity.

Mouse gamma delta T cell hybridomas from various strains that express a TCR-V gamma 1/V delta 6 respond weakly to an autologous Ag and more strongly to a short segment of the mycobacterial heat shock protein-60 (HSP-60). However, V gamma 1/V delta 6 hybridomas derived from AKR mice show greatly reduced or absent responses to these stimuli. To determine whether the lack of response in these AKR hybridomas is caused by polymorphisms found in the expressed AKR gamma and TCR-delta genes or, instead, stems from other genes in AKR, we crossed an AKR mouse with a responder mouse, C57BL/10 (B10), and prepared hybridomas from F1 progeny. Expression of an AKR V gamma 1-J gamma 4-C gamma 4 gene correlated with nonresponsiveness, whereas expression of a B10 V gamma 1-J gamma 4-C gamma 4 gene in most hybridomas ensured responses to both self Ag and the HSP-60 peptide. An allelic difference in the expressed V gamma 6 gene was irrelevant to these responses. Moreover, transfection of a functional B10 V gamma 1-J gamma 4-C gamma 4 gene into an F1 hybridoma variant that had lost the AKR version of this gene restored responses. The allelic gamma gene products differ at nine amino acids in the V region, and three amino acids in the C region. In addition, the AKR C gamma 4 region contains a 16-amino acid insertion. We propose that amino acid differences among those encoded by the AKR V gamma 1-J gamma 4-C gamma 4 gene are responsible for the lack of response, and reduce the ability of the TCR-gamma delta to bind the relevant Ag.