Specificity and function of T cells bearing gamma delta receptors

Gamma delta T cells are decreased in the blood of children with Bordetella pertussis infection

The biological role of T cell receptor (TCR) gamma delta bearing cells is not yet fully understood. We studied 12 children with Bordetella pertussis infection and 12 age- and sex-matched healthy controls. Patients with whooping-cough yielded significantly lower relative and absolute numbers of blood TCR-gamma delta + cells than normal controls (both p < 0.001). It is suggested that the depletion of circulating gamma delta T cells in patients with Bordetella pertussis infection might be the result of the dispatch of these cells to the site of inflammation, i.e. the bronchial mucosa. Interestingly, other human lung diseases, such as allergic bronchial asthma and sarcoidosis display similar pulmonary phenotypical features.

Immunohistochemical study of tumor-infiltrating lymphocytes before and after intravesical bacillus Calmette-Guérin treatment for superficial bladder cancer

BACKGROUND

This study investigated changes in the phenotypic characteristics of tumor-infiltrating lymphocytes during intravesical bacillus Calmette-Guérin (BCG) treatment using an immunohistochemical technique.

METHODS

A total of 16 patients with superficial bladder cancer underwent intravesical BCG treatment for therapeutic purposes. Tissue specimens were obtained from these patients before and after BCG treatment by cold cup biopsies.

RESULTS

The numbers of CD3+ cells, CD4+ cells, CD8+ cells, and CD19+ cells significantly increased after treatment compared with numbers before treatment (P < 0.01). Although gamma/delta T cells were not observed before treatment, they appeared after treatment in 6 patients. In all these patients, the tumors disappeared or their size was reduced by more than 50%, and none of the tumors recurred. The induction of CD25+ cells after treatment was seen in 11 of the 16 patients.

CONCLUSION

gamma/delta T cells may play an important role in the immune response of the host to the tumor in intravesical BCG treatment (although this correlation was statistically insignificant.

Gamma delta T-cell help in responses to pathogens and in the development of systemic autoimmunity

Mice rendered deficient in alpha beta T-cells by single-gene knockout mutation show enhanced levels of autoantibody formation and even some symptoms of autoimmune disease. This is remarkable given that most experimental studies heretofore have indicated that the development of autoimmune disease is highly multigenic, requiring the complementary actions of multiple loci. The basis of the phenomenon in alpha beta T-cell-deficient mice appears to be the provision of help to B-cells by other cells, including gamma delta T-cells. Perhaps surprisingly, gamma delta T-cell help seems quite efficacious, particularly after infection, when it can culminate in the formation of germinal centers. Furthermore, two independent sets of studies reviewed here indicate that significant levels of self-reactive IgG can also be provoked by gamma delta T-cells independent of germinal center formation. The task ahead is to integrate this pathway into the physiologic immune responses to healthy individuals, immunocompromised individuals, and newborns.

Duodenal intraepithelial and lamina propria T lymphocytes in human immunodeficiency virus-infected patients with and without diarrhoea

BACKGROUND

Diarrhoea is an important problem in human immunodeficiency virus (HIV)-infected patients. Intestinal pathologic conditions may arise from changes in local immunocyte populations. The aims of our study were to establish the histologic features of the duodenal mucosa of HIV-infected patients and to determine a) the phenotype of small-intestinal-intraepithelial (IELs) and lamina propria (LPLs)-lymphocytes; b) their degree of activation and differentiation within the lamina propria; and c) their relation to the presence of diarrhoea.

METHODS

Distal duodenal biopsy specimens were obtained prospectively from 29 HIV-infected patients-11 patients with diarrhoea (group 1) and 18 patients without diarrhoea (group 2)- and from 42 patients who had neither any risk factor for HIV nor diarrhoea (group 3). Histopathologic and immunohistochemical studies were combined with flow cytometric analysis, after separation of the mucosal intraepithelial compartment from the lamina propria.

RESULTS

The median number of IELs and the percentage of gamma delta IELs were both unchanged in HIV-infected patients as compared with controls. In HIV-infected patients LP CD4 cells were decreased, and LP CD8 cells increased. No significant difference was found in the expression of CD25 or CD27 within the LP CD8 populations of HIV-infected patients in groups 1 and 2.

CONCLUSIONS

These findings suggest that the occurrence of diarrhoea in HIV-infected patients is unrelated to IEL and LPL phenotype.

Phenotypical characterization of lymphocytes infiltrating regressing papillomas

Papillomavirus-induced lesions often regress spontaneously in both humans and animals. Papilloma regression is deemed to be due to a cell-mediated immune response, the nature of which is still ill defined, and is accompanied by immune cell infiltrates. To gain further information on the nature and role of the immune cells present in regressing papillomas, we have analyzed biopsies of papillomas induced in the soft palate of cattle by bovine papillomavirus type 4 (BPV-4) and have phenotypically characterized and quantified the lymphocytes present in these lesions. Eleven papilloma biopsies and seven biopsies of noninfected palate were analyzed for the presence of activated CD4+, CD8+, and gamma delta(WC1+) lymphocytes. We found large numbers of lymphocytes in the subepithelial derma of papillomas but not in normal palate tissue; these cellular masses consisted predominantly of CD4+ lymphocytes, with only a few CD8+ and gamma delta(WC1+) lymphocytes, generally positioned at the periphery of these masses. All three subtypes of lymphocytes were found interdigitated with the cells of the basal layer both in papillomas and in normal palate tissue, but while basal layer CD8+ and gamma delta(WC1+) T cells were detected with similar frequencies in papillomas and uninfected palate, basal layer CD4+ T cells were much more frequent in papillomas. CD4+, CD8+, and gamma delta(WC1+) lymphocytes were found in the suprabasal layers of papillomas, but the CD8+ and gamma delta(WC1+) T cells were more numerous and had migrated further into the differentiating keratinocytes of the papilloma fronds than the CD4+ T cells. We conclude that T-cell infiltration is characteristic of regressing BPV-4 papillomas, that CD4+ lymphocytes are specifically and massively recruited into the regressing papillomas, and that although all three lymphocyte subsets can penetrate the papilloma, only the CD8+ and gamma delta(WC1+) lymphocytes are able to migrate into the fronds. These results suggest that all three lymphocyte subsets have an important role to fulfill during natural regression of papillomas.

Clinical and pathological heterogeneity in cutaneous gamma-delta T-cell lymphoma: a report of three cases and a review of the literature

Cutaneous gamma-delta (gamma delta) T-cell lymphoma is rare. Eleven cases have been reported to date including four cases of mycosis fungoides (MF), two of pagetoid reticulosis and five of pleomorphic cutaneous T-cell lymphoma (CTCL). We report three further cases of cutaneous gamma delta T-cell lymphoma; one of MF, one of a pleomorphic CTCL and one of a subcutaneous T-cell lymphoma. Combined data suggest that although cutaneous gamma delta T-cell lymphomas do not appear to comprise a single clinicopathological entity, they may be associated with aggressive clinical behaviour and a poor prognosis.

Heterogeneity of mast cells and T cells in the nasal mucosa

Allergic diseases like atopic rhinitis, bronchial asthma, and urticaria are prevalent and on the rise. The need to better understand the pathophysiology of these diseases is therefore crucial to the development of newer and more effective modes of treatment. We hypothesized that in inflammatory diseases like allergic rhinitis and asthma characterized by profound local clinical manifestations and inflammation of the relevant mucosae, the most important immunopathological findings must occur locally. Although studies on the cellular elements and mediators in the peripheral blood compartment may provide useful information, they may not accurately reflect events occurring within the target organ itself. Even in the normal mucosa there is a resident population of lymphocytes and mast cells. Taking perennial allergic rhinitis (PAR) and chronic infective rhinitis (CIR) as representative chronic airway inflammatory diseases we investigated the phenotypic and functional characteristics of mast cells and lymphocytes in the nasal mucosa of patients with PAR and CIR during the natural course of the disease. We further compared the characteristics of lymphocytes in the nasal mucosa with that in the peripheral blood compartment. Our results demonstrated heterogeneity of mast cells and T cells in the nasal mucosa. Furthermore, the mucosal changes at the site of allergic inflammation were characterized by an increase in the proportion of CD4+ CD45RO+ T cells (memory cells); oligoclonal expansion and activation of V gamma 1/V delta 1+ T cells; an increased number of Fc epsilon RI+ cells; an increased proportion of TH2-type cytokine expressing mast cells and lymphocytes and of very late antigen-4 and very late antigen-5 expressing nasal mast cells, independent of alterations in CIR; and autologous peripheral blood. These findings strongly suggest heterogeneity of lymphocytes and mast cells in the nasal mucosa based on the underlying inflammatory disease, and compartmentalization of inflammatory cells in the nasal mucosa and peripheral blood.

T cell antigen receptor expression by intra-epithelial lymphocytes in oral lichen planus

The distribution of T lymphocytes expressing the alpha beta or gamma delta heterodimer of the T cell receptor (TCR) was examined in normal oral mucosa (NOM) and reticular oral lichen planus (OLP) using a panel of antibodies specific for CD3, the alpha beta TCR and the gamma delta TCR. Intra-epithelial lymphocytes were counted and epithelial surface length was measured by image analysis. T cells in the lamina propria were not quantified. Total intra-epithelial lymphocytes were increased in OLP compared with NOM (P = 0.0004). The proportions of cells expressing the gamma delta TCR in NOM and OLP were 10% and 9.3%, respectively, suggesting there is no selective recruitment from the circulation of either alpha beta or gamma delta TCR-bearing cells into normal oral epithelium or that affected by OLP. The role, if any, of gamma delta T cells in the pathogenesis of OLP remains to be determined.

T-cell alpha beta + and gamma delta + deficient mice display abnormal but distinct phenotypes toward a natural, widespread infection of the intestinal epithelium

Vertebrate immune systems contain T cells bearing either alpha beta or gamma delta T-cell antigen receptors (TCRs). alpha beta T cells perform all well-characterized T-cell effector functions, while the biological functions of gamma delta + cells remain unclear. Of particular interest is the role of gamma delta + cells during epithelial infections, since gamma delta + cells are commonly abundant within epithelia. Eimeria spp. are intracellular protozoa that infect epithelia of most vertebrates, causing coccidiosis. This study shows that in response to Eimeria vermiformis, mice lacking alpha beta T cells display defects in protective immunity, while mice lacking gamma delta + cells display exaggerated intestinal damage, apparently due to a failure to regulate the consequences of the alpha beta T cell response. An immuno-downregulatory role during infection, and during autoimmune disease, may be a general one for gamma delta + cells.

Antigen-driven shedding of L-selectin from human gamma delta T cells

Activation of lymphocytes leads to the modulation of a number of surface molecules. We have investigated the expression of one such molecule. L-selectin, following activation of gamma delta T cells with Mycobacterium tuberculosis. L-selectin is modulated during lymphocyte entry into lymph nodes; this modulation reflects the recirculation and homing potential of lymphocytes. We find that stimulation of gamma delta T cells by M. tuberculosis antigens results in shedding of L-selectin from gamma delta T cells. Re-expression of L-selectin occurs on removal of antigen suggesting that the regulation of expression is controlled by the presence or absence of antigen. The gamma delta T-cell receptor (TCR)-positive, L-selectin negative population of peripheral blood lymphocytes appears to be resting cells, as assessed by forward- and light-scatter analysis. We further find that gamma delta T cells isolated from a site of infection, the pleural fluid of a tuberculosis patient, are L-selectin negative, and that L-selectin is re-expressed following culture of the pleural fluid gamma delta T cells in the absence of antigen. These results demonstrate that, in addition to stimulation with polyclonal mitogens, antigen stimulation can also promote the surface shedding of L-selectin and that gamma delta T cells have the potential to home to sites of infection supporting their role in the immunological defence against infectious micro-organisms.

Sarcoidosis and common variable immunodeficiency. Report of 8 cases and review of the literature

The true incidence of sarcoidosis in common variable immunodeficiency (CVID) is unknown. We report here 8 cases of sarcoidosis among 80 patients with CVID followed in our clinics, along with 22 well-documented cases reported in the literature. Sarcoidosis, therefore, represents an important entity to consider among patients with CVID who exhibit clinical, radiographic, laboratory, and biopsy findings compatible with sarcoidosis. Conversely, the diagnosis of CVID should be considered in patients with sarcoidosis who do not exhibit the characteristic hypergammaglobulinemia and who have a history of recurrent infections. Although many features of sarcoidosis are similar in patients with CVID to those in patients with sarcoidosis alone, there are many important differences. Patients with CVID in whom sarcoidosis develops present with hypogammaglobulinemia rather than hypergammaglobulinemia and have a higher prevalence of recurrent infections, thrombocytopenia, and splenic involvement. Steroids, in most cases, appeared helpful in reducing adenopathy and splenomegaly, improving uveitis, lowering serum alkaline phosphatase, and reversing hematologic abnormalities. The underlying pathophysiology responsible for the association of these 2 disorders in the same patient remains obscure. However, as more patients are identified, it may be possible to gain a better understanding of the immunologic defect responsible for the dual presentation of these 2 relatively uncommon diseases.

Lymphocyte subpopulations in the mammary gland of the goat

Mammary glands of pregnant, lactating and resting goats were studied by immunohistochemistry for lymphocyte subpopulations using a panel of monoclonal antibodies. All T lymphocyte subpopulations that may have a role in the immune response, CD2+, CD4+, CD8+ and gamma delta T cells and subsets, were present in the mammary gland and were noted to increase in number progressively during pregnancy, decrease significantly during lactation, and then moderately increase during the resting period. CD4+ cells, the predominant cell type in the mammary gland, were located mainly in the connective tissue, whereas CD2+, CD8+ and TcR1-N24+ cells were predominant in the intraepithelial areas. TcR1-N6+ cells were detected almost exclusively during pregnancy, being localized mainly in the connective tissue. Their proportion decreased markedly following parturition. Very few WC1-N3+ and -N4+ cells were detected in the mammary gland. It is suggested that the majority of gamma delta T lymphocytes in the mammary gland of the goat are CD2+ CD8+ WCl-, a distinctive subset from that of the WCl+ subset in peripheral blood.

Avian gut-associated lymphoid tissues and intestinal immune responses to Eimeria parasites

Coccidiosis, an intestinal infection caused by intracellular protozoan parasites belonging to several different species of Eimeria, seriously impairs the growth and feed utilization of livestock and poultry. Host immune responses to coccidial infection are complex. Animals infected with Eimeria spp. produce parasite-specific antibodies in both the circulation and mucosal secretions. However, it appears that antibody-mediated responses play a minor role in protection against coccidiosis. Furthermore, there is increasing evidence that cell-mediated immunity plays a major role in resistance to infection. T lymphocytes appear to respond to coccidial infection through both cytokine production and a direct cytotoxic attack on infected cells. The exact mechanisms by which T cells eliminate the parasites, however, remain unclear. Although limited information is available on the intestinal immune system of chickens, gut lymphoid tissues have evolved specialized features that reflect their role as the first line of defense at mucosal surfaces, including both immunoregulatory cells and effector cells. This review summarizes our current understanding of the avian intestinal immune system and mucosal immune responses to Eimeria spp., providing an overview of the complex cellular and molecular events involved in intestinal immune responses to enteric pathogens.

Alpha/beta- and gamma/delta-T-cell-receptor-positive lymphocytes in healthy and inflamed human conjunctiva

BACKGROUND

The possible existence and distribution patterns of alpha/beta- and gamma/delta-TCR+ cells, which are important constituents of immune surveillance and act via the CD3+ cell complex have not yet been elucidated in the healthy and inflamed conjunctiva.

MATERIALS AND METHODS

Paraffin-embedded conjunctival specimens included 18 from 18 patients with ocular cicatricial pemphigoid (OCP), 20 from 20 healthy controls, 6 from 6 patients with lye burns, and 6 from 2 patients with Stevens-Johnson syndrome; all were worked up by histology and immunohistochemistry.

RESULTS

alpha/beta-TCR+ cells were visualized in the conjunctival epithelium and stroma of healthy persons, OCP, lye burns and Stevens-Johnson syndrome. alpha/ beta-TCR+ cells and a small number of gamma/delta-TCR+ cells were observed in the corneal epithelium and stroma of patients who have failing corneal grafts. After ileal mucosa transplantation to the epibulbar conjunctiva, membrane staining changes to nuclear and cytoplasmic staining. Treatment with systemic cytotoxic drugs abolishes all alpha/beta-TCR+ and gamma/delta-TCR+ cells.

CONCLUSIONS

alpha/beta-TCR+ cells can be found in the non-infected epithelium and stroma of the healthy and inflamed (OCP, lye burns, and Stevens-Johnson syndrome) conjunctiva, as well as in the corneal epithelium and stroma of failing corneal grafts, whereas gamma/delta-TCR+ cells are absent. A small number of gamma/delta-TCR+ cells are present in the corneal stroma and adjacent conjunctival epithelium of patients with chronic corneal graft rejection or after transplantation of gut tissue. Further investigations may establish the role, if any, of these T-cell subsets in immune surveillance of the non-infected outer eye and in corneal graft rejection.

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.

Intraepithelial gamma/delta T cells in duodenal mucosa are related to the immune state and survival time in AIDS

The proportion of T-cell receptor gamma/delta+ cells and the CD4/CD8 ratio relative to all CD3+ intraepithelial lymphocytes (IEL) were determined by immunofluorescence in duodenal mucosa of late-stage (mostly CDC IVC1/D) subjects (n = 21) infected with human immunodeficiency virus type 1 (HIV-1). The gamma/delta fraction (median, 14.2%; range, 1.7 to 59.8%) was increased (P < 0.03) compared with that in HIV- controls (n = 11; median 2.8%; range, 0.3 to 38%). Also, the number of gamma/delta+ IEL per mucosal unit was increased (P < 0.05) in the HIV+ subjects (median, 11.1/U) compared with the controls (3.2/U). Approximately 100% of the gamma/delta+ IEL were CD8-, and most expressed the Vdelta1vJdelta1-encoded epitope (median, 90.9%). The total number of CD3+ IEL tended to be lower than in the controls (67.4 versus 72.9/U). Both the epithelium and the lamina propria contained mainly CD8+ T cells, the median ratios of CD4+ T cells being 1 and 7.6%, respectively. This result accorded with the reduced CD4 cell number in blood (median, 18 X 10(6)/liter). The HIV+ subjects had increased serum levels of neopterin and beta2-microglobulin (both P < 0.0001), probably reflecting immunostimulation. Serum neopterin and beta2-microglobulin were inversely related to duodenal gamma/delta IEL, particularly in the premortal group (r = -0.97 and r = -0.58, respectively). The increased gamma/delta IEL might reflect enhanced intestinal protection in late-phase HIV infection. Short survival expectancy (<7 months) was associated not only with high levels of neopterin and beta2-microglobulin but also with a reduced number of duodenal gamma/delta+ cells (P < 0.03).

Necrotizing enterocolitis: the search for a unifying pathogenic theory leading to prevention

During the past two decades, necrotizing enterocolitis has emerged as a major cause of mortality and morbidity in premature infants. The specific cause of the disease remains enigmatic, but several putative risk factors provide clues to a pathophysiology that seems to be multifactorial. With the use of newly developed scientific tools, an understanding of the basic pathophysiologic cascade that causes necrotizing enterocolitis is emerging, providing hope for improved treatment and prevention.

Resistance to cutaneous graft-vs.-host disease is not induced in T cell receptor delta gene-mutant mice

The function of murine dendritic epidermal cells (dEC) remains largely speculative, probably because of the lack of a suitable in vivo model, although previous studies suggest that gamma/delta+ dEC may have originally evolved to serve as a self-protection mechanism(s). Our previous study demonstrated that the epidermis of mice that had spontaneously recovered from cutaneous graft-vs-host disease (GVHD) induced by local injection of CD4+ autoreactive T cells contained unexpectedly large numbers of dEC and became resistant to subsequent attempts to induce GVHD in a site-restricted manner, suggesting that the resistance is mediated by dEC. However, because alpha/beta+ dEC as well as gamma/delta+ dEC were greatly increased in number in the epidermis, it was unclear whether gamma/delta+ dEC are indeed responsible for this protection. The availability of this murine model and mice selectively lacking gamma/delta T cells as a result of disruption of the T cell receptor C delta gene segment allowed us to investigate the role of gamma/delta+ dEC. In the epidermis of gamma/delta T cell-deficient mice (delta-/-), a congenital lack of gamma/delta+ dEC was substituted for by alpha/beta+ dEC of either a CD4-8+ or a CD4-8- phenotype. After intradermal injection of the autoreactive T cells, delta-/- mice developed significantly enhanced delayed-type hypersensitivity responses and cutaneous GVHD, which persisted longer than in heterozygous littermate controls (delta+/-). Surprisingly, resistance to the cutaneous GVHD was not induced in the epidermis of delta-/- mice after spontaneous recovery from the GVHD, whereas the "susceptible" epidermis of delta-/+ mice contained large numbers of alpha/beta dEC comparable to those in "resistant" epidermis of delta+/- mice. Injection of day 16 fetal thymocytes from wild-type mice into delta-/- mice resulted in the appearance of donor-type gamma/delta+ dEC in the epidermis, and reconstitution with gamma/delta+ dEC restored the protective immune response of the epidermis against the GVHD to nearly normal levels. These results indicate that gamma/delta+ dEC are responsible for the site-restricted protection against cutaneous GVHD.

gamma/delta and other unconventional T lymphocytes: what do they see and what do they do?

T lymphocytes recognize specific ligands by clonally distributed T-cell receptors (TCR). In humans and most animals, the vast majority of T cells express a TCR composed of an alpha chain and a beta chain, whereas a minor T-cell population is characterized by the TCR gamma/delta. Almost all of our knowledge about T cells stems from alpha/beta T cells and only now are we beginning to understand gamma/delta T cells. In contrast to conventional alpha/beta T cells, which are specific for antigenic peptides presented by gene products of the major histocompatibility complex, gamma/delta T cells directly recognize proteins and even nonproteinacious phospholigands. These findings reveal that gamma/delta T cells and alpha/beta T cells recognize antigen in a fundamentally different way and hence mitigate the dogma of exclusive peptide-major histocompatibility complex recognition by T cells. A role for gamma/delta T cells in antimicrobial immunity has been firmly established. Although some gamma/delta T cells perform effector functions, regulation of the professional and the nonprofessional immune system seems to be of at least equal importance. The prominent residence of gamma/delta T cells in epithelial tissues and the rapid mobilization of gamma/delta T cells in response to infection are consistent with such regulatory activities under physiological and pathologic conditions. Thus, although gamma/delta T cells are a minor fraction of all T cells, they are not just uninfluential kin of alpha/beta T cells but have their unique raison d'être.

Characterization of lymphocytic infiltrates in Helicobacter pylori-associated gastritis

BACKGROUND

This study evaluated the specific subset composition of lymphocytes present in Helicobacter pylori-associated gastritis (HAG), since reports so far have led to inconclusive and conflicting results.

METHODS

Endoscopic biopsy specimens from 56 patients were studied by quantitative immunohistochemistry using monoclonal antibodies against the lymphocyte markers CD3, CD22, CD4, CD8, CD45RO, CD1O3, TCR alpha/beta, and TCR gamma/delta. Lamina propria and intraepithelial compartments were evaluated separately. Grade, activity, and density of bacterial colonisation were assessed histologically and with Warthin-Starry stain.

RESULTS

Evaluation showed a significant increase in CD4+, CD45RO+, TCR alpha/beta+ activated lamina propria lymphocytes in HAG which correlated with grade and activity of gastritis and degree of bacterial colonisation, whereas subsets of intraepithelial lymphocytes did not change significantly. TCR gamma/delta+ T cells were not found to be increased in HAG.

CONCLUSIONS

Selective expansion of CD4+, CD45RO+ memory-type T cells could reflect an antigen-specific and/or chemokine-mediated effect in HAG. Locally produced CC chemokines such as RANTES have been detected in HAG.

Spondylarthropathies: from gut to target organs

Recent studies strongly support the concept that gut and joint inflammation are closely related. Progress also has been made in identifying individual mechanisms that contribute to the pathogenesis of joint disease in IBD and in undifferentiated SpAs. However, the interrelationship of these mechanisms that result in chronic disease manifestations at a site distant from the initiating event remain to be elucidated. The local absence of homing molecule receptors in the gut wall combined with an expression of these receptors in target organs can be responsible for the transformation of the synovial membrane and/or the enthesis into an aberrant tertiary lymphoid organ of the gut.

Presentation of antigens derived from microorganisms residing in host-cell vacuoles

Antigens presented by major histocompatibility complex molecules have been classified into those presented by 'endogenous' and 'exogenous' pathways. Some microorganisms reside within host-cell vacuoles that appear to avoid both pathways. Novel presentation mechanisms are being unraveled for these microorganisms, and their antigens, rather than being just peptides, can also consist of lipids or DNA fragments.

Ontogenic development and tissue distribution of V gamma 1-expressing gamma/delta T lymphocytes in normal mice

A hamster monoclonal antibody (mAb) recognizing an epitope in the V gamma 1-J gamma 4-C gamma 4 chain of the gamma/delta T cell receptor has been generated. Using this mAb, we have quantitated the occurrence of V gamma 1-bearing gamma/delta T cells in the developing thymus and in the lymphoid organs and several epithelia of adult mice. The V gamma 1-expressing cells constitute a minor gamma/delta T cell subpopulation during fetal and early postnatal life, but they constitute a major population of gamma/delta T cells in the thymus and in the peripheral lymphoid organs in adult mice. In addition, we found that V gamma 1-bearing cells comprise a large proportion (15-60%) of the gamma/delta T cells present in the intestinal epithelium (i-IEL) in all strains of mice tested. V gamma 1+ i-IEL are present in athymic (nude) mice and in antigen-free mice, demonstrating that they can develop extrathymically and that their presence in the intestinal epithelium is independent of the antigenic load of the gut. Our results show that V gamma 1-bearing lymphocytes account for the largest population of gamma/delta T cells in the mouse. This population includes a thymus-dependent component that homes to the secondary lymphoid organs and a thymus-independent component that constitutes a major fraction of the gamma/delta i-IELs.

Immunity and immunopathology to respiratory syncytial virus. The mouse model

Infection with respiratory syncytial virus (RSV) is a major unsolved challenge for vaccine development. RSV is worldwide in distribution and infects almost all children during the first 2 yr of life. The mouse model of RSV lung disease has been very successful in reproducing many aspects of the human disease. In particular, the role of antiviral T cells in both eliminating virus and causing enhanced disease has been shown dramatically. This immunopathologic paradox is now more clearly understood than for any other common human infection, largely due to insights gained from the mouse model. This review focuses on the unique ability of different RSV proteins to prime for specific functional subsets in the mouse, and the association between sensitization to the major surface glycoprotein G, the induction of T helper 2 cells, and the subsequent appearance of lung eosinophilia during RSV infection.

Peripheral gamma delta T-cell populations in HIV-infected individuals with mycobacterial infection

Previous studies have suggested that gamma delta T cells can be increased in HIV-1-seropositive individuals, although characterization of gamma delta T cell subtypes and correlation with clinical status of these patients have not been performed. We investigated groups of HIV-seropositive persons to determine the prevalence of elevated levels of gamma delta T cells and whether any gamma delta T cell subtypes were preferentially expressed. Since a large proportion of human gamma delta T cells appear to be reactive to proteins encoded by mycobacteria, we also examined our patients for the incidence of mycobacterial infection. Our results show that a significant number of HIV-positive patients have an elevated number of gamma delta T cells in their peripheral blood as compared to normal controls. HIV-seropositive patients with clinical or laboratory evidence of mycobacterial infection had statistically significant increases in the percentage and total numbers of gamma delta T cells over the HIV-positive persons without mycobacterial infection. An examination of the subtypes of gamma delta T cells revealed that certain subtypes such as V gamma 9+ and V delta 2+ T cells were preferentially elevated in the mycobacteria-positive patients. These results suggest that an increased number of gamma delta T cells in HIV-positive patients is most often seen in the setting of an opportunistic mycobacterial infection and that specific gamma delta T cell subtypes are stimulated under these conditions. The role of these increased number of gamma delta T cells in HIV-associated disease is unclear but is likely a component of the response and degree of host resistance to this organism.

Scarcity of gamma delta T cells in intestinal epithelia containing coccidia despite general increase of epithelial lymphocytes

Lymphocytes of intestinal epithelia were examined in lambs experimentally infected with coccidia. Fourteen conventional, coccidia-free 3-week-old lambs of the Dala breed were given either 250,000 (eight lambs in experiment 1) or 100,000 (six lambs in experiment 2) sporulated oocysts of Eimeria ovinoidalis (> 99.9% pure) via a stomach tube. Nine lambs (five in experiment 1 and four in experiment 2) of the same age served as uninoculated controls. The infected lambs developed diarrhea and dehydration between days 10 and 13 after infection. Intestinal specimens were collected 10-20 days after inoculation. A heavy multifocal infection of the epithelium comprising schizonts, gamonts, and oocysts resulted, with changes being most pronounced in the large intestine and the terminal part of ileum. Lesions included villous atrophy, villous fusions, and crypt hyperplasia. Computer-assisted morphometric analysis was applied to immunoperoxidase-stained sections for quantification of intraepithelial T cell subsets and included the distal jejunum of lambs of experiment 1. A significant increase in the epithelial area of the distal jejunum occupied by CD8+ lymphocytes was found in the infected lambs as compared with uninfected controls (18.3% versus 3.7%). The increased presence of CD8+ cells may be of significance in the intestinal immune response to ovine coccidiosis. A moderate, overall increase was also found for the gamma delta lymphocytes in the jejunal epithelium. Examination of the ileum of infected lambs of both experiments showed a scarcity of gamma delta cells (0.4% of epithelial area) in stretches of epithelium infected by coccida as compared with adjacent noninfected epithelium (4.0% of epithelial area).(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of gamma delta T cell receptor on caprine globule leukocytes

Histochemical characteristics and immunological surface phenotypes of globule leukocytes (GLs) of normal goats were investigated in the intestine. In the small intestine, GLs were concentrated in the base of the villus and around the crypt, whereas in the cecum and colon they were randomly distributed. Their cytoplasmic granules exclusively stained with phosphotungstic acid hematoxylin, and were negative for peroxidase and histamine in contrast to those of subepithelial mast cells. The existence of chondroitin sulfate in some granules of GLs and heparin in most granules of mast cells were revealed by alcian blue staining and digestion with chondroitinase ABC. Isolated intestinal GLs were positive for T cell receptor (TcR) 1-N24 (gamma delta) and CD8 alpha, and negative for WC1-N3 and WC1-N4. Cryostat sections of ileum revealed preferential intraepithelial distribution of both TcR1-N24+ cells and CD8+ cells. WC1-N3+ and WC1-N4+ cells were rarely seen in the epithelium and lamina propria. These results indicate that caprine GLs are a gamma delta T cell subset, which is a different cell population from WC1 positive gamma delta T cells.

The enigmatic specificity of gamma delta T cells

In most scientific investigations, the study of mechanism follows the study of function. For example, alpha beta T cells were shown to be important mediators of immunity before the interaction between the T cell receptor (TCR) and peptide-MHC complexes was understood. However, sometimes the study of function follows from the study of mechanism. Research of gamma delta T cell receptors falls into this category. The gamma chain of the TCR was first cloned in 1984, which then led to the discovery of gamma delta T cells in 1985. Since then, research has focused on understanding ligands of the gamma delta TCR with the hope of better understanding the function of gamma delta T cells. An initial assumption was that gamma delta T cells, like alpha beta T cells, recognize peptides bound to MHC molecules; however, recent data indicate that gamma delta T cells are not biased towards MHC recognition in the same way as alpha beta T cells. Although there are intriguing new insights, the specificity and function of gamma delta T cells remains a mystery.

Chicken thymic nurse cells: an overview

Thymic nurse cells are multicellular complexes located in the subcortical area of the thymus of all avian, mammalian and amphibian species investigated so far. Since their first description in 1980 many studies have been carried out to characterize their morphological and functional properties. The purpose of this review is to summarize recent morphological as well a functional analyses of chicken thymic nurse cells which suggest a role of these cell complexes in T cell selection.

Preferential activation and expansion of human peripheral blood gamma delta T cells in response to Toxoplasma gondii in vitro and their cytokine production and cytotoxic activity against T. gondii-infected cells

Studies were conducted to determine if gamma delta T cells participate in the immune response to Toxoplasma gondii. Preferential expansion of human gamma delta T cells occurred when peripheral blood T cells from either T. gondii-seronegative or seropositive individuals were incubated with autologous PBMC infected with the parasite. That gamma delta T cells proliferated after incubation with infected cells was confirmed using purified of gamma delta T cells. These T. gondii-induced gamma delta T cell responses did not require prior exposure to the parasite since T cells obtained from umbilical cord blood from seronegative newborns also exhibited preferential expansion of gamma delta T cells. Cytofluorometric analysis of T cells obtained from either umbilical cord blood or peripheral blood from adults revealed that V gamma 9+ and V delta 2+ gamma delta T cells responded to stimulation with infected cells. Preferential expansion of gamma delta T cells was not restricted by polymorphic determinants of MHC molecules. PBMC that had internalized killed parasites but not PBMC incubated with T. gondii lysate antigens also stimulated preferential expansion and activation of gamma delta T cells as assessed by expression of CD25 and HLA-DR molecules. V gamma 9+V delta 2+ gamma delta T cells were cytotoxic for T. gondii-infected cells in an MHC-unrestricted manner, and produced IFN-gamma, IL-2, TNF-alpha, but not IL-4 when incubated with cells infected with the parasite. These results suggest that rapid induction of a remarkable primary gamma delta T cell response may be important in the early protective immune response to T. gondii.

Immunobiology of mouse dendritic epidermal T cells: a decade later, some answers, but still more questions

Over the past decade, overwhelming evidence has accumulated in many species, most notably in mice, that epithelial sites such as skin, intestine, and reproductive tract are populated with relatively discrete subsets of gamma delta cells. Such studies have identified several distinguishing and, in some cases, unique features of the dendritic epidermal T cells (DETC) populating the skin of all normal mice: homogeneous V5-J1-C gamma 1/V1-D2-J2-C delta T-cell receptors devoid of junctional diversity, apparent tissue restriction in adult mice to the skin, an important role for active hair growth in their localization and/or proliferation in the skin, and a capacity to recognize an antigen expressed on stressed epidermal cells. These properties have led to the hypothesis that DETC play distinctive roles in cutaneous immune surveillance and/or immunoregulation via recognition of a common self-antigen expressed by adjacent cells under various potentially harmful circumstances. Despite substantive advances in our knowledge about gamma delta cells in general (e.g., recent evidence that their manner of antigen recognition may be fundamentally different from that used by conventional alpha beta T cells) and about epithelial-specific subsets such as murine DETC in particular, it is clear that, compared with our understanding of alpha beta cells, major gaps still exist in our understanding of these cells. Persisting questions about DETC include: precise identification of the ligands for their homogenous T-cell receptors, the cellular and molecular requirements for their activation, their full range of functional activities, the reason(s) for the absence in normal human skin of a precise morphologic and phenotypic homologue, and, perhaps most important, their biologically relevant role(s) in cutaneous physiology, immunity, and/or pathology.

Homeostatic regulation of intestinal epithelia by intraepithelial gamma delta T cells

Although T cells bearing gamma delta T-cell receptors have long been known to be present in the epithelial lining of many organs, their specificity and function remain elusive. In the present study, we examined the intestinal epithelia of T-cell-receptor mutant mice, which were deficient in either gamma delta T cells or alpha beta T cells, and of normal littermates. The absence of gamma delta T cells was associated with a reduction in epithelial cell turnover and a downregulation of the expression of major histocompatibility complex class II molecules. No such effects were observed in alpha beta T-cell-deficient mice. These findings indicate that intraepithelial gamma delta T cells regulate the generation and differentiation of intestinal epithelial cells.

Interleukin 7 is produced by human intestinal epithelial cells and regulates the proliferation of intestinal mucosal lymphocytes

The interaction of mucosal lymphocytes and intestinal epithelial cells is thought to be important in regulating immune response in the intestinal mucosa, but conclusive evidence is limited. Here we demonstrate the expression of IL-7 mRNA in human intestinal mucosa by combined reverse transcription PCR and Southern blot hybridization. Immunohistochemistry and in situ hybridization confirm the presence of IL-7 in intestinal epithelial cells, especially in epithelial goblet cells. Moreover, IL-7 receptor expression in mucosal lymphocytes is demonstrated by immunohistochemistry and in situ hybridization, as well as by Southern blot and flow cytometric analysis of freshly isolated lamina propria lymphocytes. In contrast, IL-7 receptor could not be detected in the cell surface of freshly isolated PBLs. The functional activity of IL-7 receptor is demonstrated by the utility of recombinant IL-7 to stimulate the growth of lamina propria lymphocytes, and conversely inhibit CD3-dependent proliferation of these cells. In contrast, IL-7 caused no significant increase in DNA synthesis and cell numbers when added to PBLs. These findings suggest that human intestinal epithelial cells and epithelial goblet cells produce IL-7, and locally produced IL-7 may serve as a potent regulatory factor for intestinal mucosal lymphocytes.

The distribution of lymphocyte subpopulations in normal and acanthotic ovine skin

The prevalence and distribution of lymphocyte subpopulations in normal and acanthotic ovine skin were investigated using monoclonal antibody immunocytochemistry. CD8+ cells were predominant in the epidermis of both normal and acanthotic skin, but were CD8+ cells, CD4+ cells and T19+ cells infrequent in normal epidermis. Within the dermis of normal skin, there were significantly greater numbers of CD4+ and T19+ cells situated around the superficial dermal vessels than in any other region examined. The majority of the CD8+ cells adjoined vessels, but the proportion that did not was greater for CD8+ than for CD4+ or T19+ cells. The CD4+ and CD8+ subsets were represented equally in adnexa. T cells were of memory phenotype. B cells and naive T cells, both of which express the CD45RA antigen, were rarely seen and tended to be associated with vessels in both normal and acanthotic skin. None of the T19+ cells (which are gamma delta+) resembled the dendritic gamma delta cells seen in murine epidermis. Acanthotic skin was strikingly different to normal skin. There was a greater abundance of T cells, particularly CD4+ cells, in acanthotic epidermis and the numbers of CD8+ and T19+ cells, and to a greater extent CD4+ cells, were greater at the dermal-epidermal junction. There were more CD4+ and CD8+ cells in the superficial dermal stroma of acanthotic skin. Within the dermis of acanthotic skin, T cells were concentrated near vessels but the apportioning of T cells between stromal/adnexal and vessel-associated sites differed from normal. Such observations suggest that migration away from perivascular sites and into the stroma may be controlled separately for subregions of skin and for each T cell subset. The role of this altered nonrandom migration of T cells in skin chronically exposed to ultra violet radiation is uncertain.

Intestinal T lymphocytes

The intestine is largely colonized by bacteria and further exposed to an immense array of ingested and shed immunogenic material. Therefore, the gut associated lymphoid tissue plays a major role in the human immune system. It may even constitute a unique immune system of its own, since it has been demonstrated to differ anatomically, phenotypically, functionally and on a molecular basis from its systemic counterpart and other peripheral lymphoid tissue. This is ultimately reflected by the observation in (transgenic) mice that intraepithelial T cells can develop independently of the thymus. Along the same lines, a rapidly growing body of evidences suggests that human bone marrow precursors can home to the gut epithelium, rearrange their T cell receptor genes and further differentiate in the mucosal micro environment. This, and other features that characterize the 'diffuse' mucosal T cell infiltrate will be discussed.

Cutaneous findings in HIV-1-positive patients: a 42-month prospective study. Military Medical Consortium for the Advancement of Retroviral Research (MMCARR)

BACKGROUND

Cutaneous disease is common in patients infected with HIV-1.

OBJECTIVE

The aim of our study was to identify cutaneous markers associated with HIV-1 infection and disease progression as measured by Walter Reed (WR) stage.

METHODS

For 42 months we have observed 912 HIV-1-positive patients in all WR stages. All patients had an extensive past and present medical history taken as well as a complete physical examination, periodic visits, and appropriate diagnostic procedures.

RESULTS

Increasing dryness of the skin and seborrheic dermatitis are early findings in a large percentage of patients in WR stage 1; the occurrence and severity of both conditions increase with disease progression. Tinea infections, condylomata acuminata, and verrucae are seen early, but with disease progression, although there is no clear increase in occurrence, these infections become more diffuse and resistant to treatment. Flares in acne vulgaris and folliculitis show a peak occurrence in early and mid-stage disease with a decreased occurrence in late-stage disease. Herpes simplex infections, oral candidiasis, molluscum contagiosum, Staphylococcus aureus infections, and oral hairy leukoplakia show a marked increase in occurrence with advanced disease. Conditions that have a statistically significant association with disease progression as measured by a change in a stage include drug eruptions, seborrheic dermatitis, oral candidiasis, oral hairy leukoplakia, molluscum contagiosum, herpes zoster, and hyperpigmentation (nail, oral, skin).

CONCLUSION

The most frequent and persistent cutaneous disorders were asteatosis (with or without asteatotic eczema) and seborrheic dermatitis. Conditions that were associated with a change in WR stage include drug eruptions, seborrheic dermatitis, oral candidiasis, oral hairy leukoplakia, molluscum contagiosum, herpes zoster, and hyperpigmentation. In addition to Kaposi's sarcoma, patients with HIV-1 disease have an increased potential for the development of both cutaneous epithelial and probably melanocytic malignancies. Epithelial tumors were seen in patients in all stages of disease.

Different pattern of T cell receptor delta gene rearrangement in tumour-infiltrating lymphocytes and peripheral blood in patients with solid tumours

Tumour-infiltrating lymphocytes (TIL) and peripheral blood lymphocytes (PBL) from four patients with renal-cell carcinoma (three paired with blood), two colon carcinomas (both paired with blood) and two melanomas (blood was not available) were analysed for the T cell receptor (TCR) delta gene repertoire. Polymerase chain reaction analysis, employing a panel of specific primers for TCR delta gene segments, showed different gene rearrangement patterns in TIL and PBL in all patients. Simultaneous analysis of TIL and PBL revealed the presence of lymphoid cells in the tumour tissue that were not present in the periphery. These results demonstrate that, although tumour-infiltrating lymphocytes contain gamma/delta T cells within the range observed in peripheral blood, these cells differ from those in peripheral blood in their gene repertoire and this may account for selective accumulation or/and in situ amplification of gamma/delta lymphocytes at the tumour site, indicating a unique type of host reaction against tumour.

Advances in immunology

Much was accomplished in the last decade in understanding how the adaptive immune system evolved to combat pathogens. Essential features of antigen presentation and T lymphocyte recognition were deciphered, setting the stage for further studies that elucidated basic elements of lymphocyte differentiation (including positive and negative selection during lymphocyte ontogeny) and the major interactions that occur among cells in secondary lymphoid organs in an ongoing immune response. The major challenges of today are found in the burgeoning fields of programmed cells death, enzymology of recombination and somatic mutation, development of memory, and the recognition of pathogens by unconventional lymphocytes.

V delta 1+ gamma/delta T lymphocytes infiltrating human lung cancer express the CD8 alpha/alpha homodimer

Murine gamma/delta T lymphocytes localize to different epithelial tissues and are phenotypically distinct from peripheral gamma/delta T cell-populations in that they show limited TCR diversity, express the CD8 alpha/alpha homodimer and lack the CD8 beta chain. In humans, a compartmentalization of gamma/delta cells sharing similar phenotypic features has been documented to date only in the case of intestinal epithelium. In the present study we show that about half of V delta 1+ (as well as V delta 1-V delta 2-) gamma/delta lymphocytes, which can be selectively expanded from human lung cancers, coexpress the CD8 alpha/alpha homodimer. The accumulation of intraepithelial CD8+ gamma/delta+ lymphocytes might then be a more general phenomenon, possibly as a result of common mechanisms operating at those sites.