Human T-cell activation deficiencies

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

CD69 expression as an index of T-cell function: assay standardization, validation and use in monitoring immune recovery

BACKGROUND

CD69 is a surrogate marker of T-cell responsiveness to mitogen and Ag stimulus and can be used as a measure of T-lymphocyte activation. Quantitative flow cytometric determination of CD69 expression on T lymphocytes has several advantages over traditional lymphocyte proliferation assays, but this method has not yet been standardized for clinical applications.

METHODS

We qualified a commercially available assay using the manufacturer's procedures for measurement of T-cell response to a mitogen (PHA), superantigen (Staphylococcus endotoxin B; SEB) and Ca(2+) ionophore (phorbyl myristate acetate; PMA) with peripheral blood from healthy volunteers. Following this, we tested the usefulness of the assay in determining T-cell responses to PHA and SEB for six immunocompromised patients.

RESULTS

Healthy volunteers showed 17-fold increases in T-cell CD69 Ab bound per cell (ABC) with PHA stimulation compared with the baseline. SEB was also an effective T-cell activating agent, increasing CD69 ABC by 5-fold, comparable with results obtained with PMA stimulation. PHA- and SEB-stimulated T-cell CD69 ABC for patients 100 days post-BM transplant were generally below 1 SD of that from healthy volunteers. SEB-stimulated T-cell CD69 expression was significantly depressed for CD8(+) T cells while CD4(+) T-cell responses to SEB were generally within 1 SD of the mean for healthy volunteers.

DISCUSSION

These results suggest that quantitative measurement of CD69 surface expression by flow cytometry is a useful diagnostic tool for detailed assessment of T-lymphocyte and subset activation.

Atypical X-linked SCID phenotype associated with growth hormone hyporesponsiveness

Severe combined immunodeficiency (SCID) is a heterogeneous group of disorders characterized by defect of T- and B-cell immunity. In many cases of autosomal recessive SCID, thus far described, the molecular alteration involves genes encoding for molecules that participate in the signal transduction. We report on a patient affected by a combined immunodeficiency, characterized by severe T-cell functional impairment, in spite of a close to normal number of circulating mature type T and B cells. NK cells were absent. Associated with the immunodeficiency, this patient also showed short stature characterized by very low growth velocity, delayed bone age and absence of increase of the plasma levels of Insulin growth factor-I (IGF-I) after growth hormone (GH) in vivo stimulation indicating peripheral hyporesponsiveness to GH. Evaluation of the protein tyrosine phosphorylation events occurring following either T-cell receptor (TCR) or GH receptor (GHR) triggering revealed striking abnormalities. No molecular alteration of GHR gene was found, thus suggesting the presence of postreceptorial blockage. Mutational screening and expression analysis failed to reveal any molecular alteration of JAK2 and STAT 5 A/B genes thus ruling out the involvement of these genes in the pathogenesis of this form of SCID. Mutational analysis of IL2Rgamma chain gene revealed the presence of a L183S missense mutation, thus indicating an atypical and a more complex clinical presentation of this X-linked form of SCID. At our knowledge, this is the first report on the GH hyporesponsiveness in this disease.

Antigen-specific activation and proliferation of CD4+ and CD8+ T lymphocytes from brucellosis patients

Salt-extractable antigen from Brucella melitensis 16M (RCM-BM) was used to evaluate the immune response from acute and chronic patients suffering from Brucella infections (in Mexico); their responses were compared with those of healthy controls. As a readout we used upregulation of CD69 (a well-established early activation marker for lymphocytes), lymphocyte proliferation by 3[H]thymidine or 5-bromo-2-deoxyuridine (BrdU) incorporation measured by liquid scintillation or flow cytometry, respectively, and production of gamma interferon (IFN gamma). We compared the antigen-specific response with the response induced by phytohaemagglutinin (PHA) as a positive control. There was no difference between acute patients and the healthy controls in the percentages of CD3+, CD4+ or CD8+ lymphocytes. However, we found that chronic patients had a significant (P < 0.05) increase in the CD8+ T cells, in line with previous studies. Antigen-specific responses to RCM-BM showed a significant (P < 0.05) upregulation of CD69 in both CD4+ and CD8+ T lymphocytes in acute brucellosis patients and in CD8+ T lymphocytes in chronic patients, indicating that both populations became activated by this antigen preparation. Moreover, lymphocyte proliferation from both acute and chronic patients in response to RCM-BM was highly significant (P < 0.001) when compared with healthy controls. However, there were no apparent differences between acute and chronic patients. Although the incorporation of BrdU showed similar results it provided additional information, since we demonstrated that both CD4+ and CD8+ T lymphocytes from acute and chronic patients proliferated equally well in response to RCM-BM. Similar results were observed with intracellular IFN gamma determination. As a whole, our data suggest an important role for both CD4+ and CD8+ T lymphocytes in Brucella infection in humans. As has been reported in mice, it is feasible that activated CD8+ T cells participate in protection against Brucella in humans through cytotoxicity or/and by the production of factors such as interferon and granulysin. The role of these cells should be carefully analysed to understand better their participation in human infection by Brucella.

Heterogeneity of host immunological risk factors in patients with aggressive periodontitis

BACKGROUND

The pathogenesis of early-onset periodontitis (EOP) can be explained by various host risk factors. Previous studies have focused on a single (among many possible) immunological risk factor and the association among the factors has not been assessed. We comprehensively investigated the associations among multiple host immunological risk factors in EOP patients to further elucidate their role in the pathogenesis of EOP.

METHODS

Sixty-eight EOP patients (50 generalized EOP, 18 localized EOP), 51 EOP-suspected patients (S-EOP), 43 adult periodontitis (AP) patients, and 36 periodontally healthy subjects (HS) participated in this cross-sectional study. We examined peripheral neutrophil functions, phenotypic and functional characterization of peripheral lymphocytes (lymphocyte subsets, T-cell proliferative activity), cytokine productivity (interleukin [IL]-1, IL-2, tumor necrosis factor [TNF]-alpha, interferon [IFN]-gamma, IL-4 and IL-6), serum immunoglobulin G (IgG) antibody titers against 12 periodontal bacteria, and HLA class II genotypes.

RESULTS

G-EOP, S-EOP, and AP patient groups showed significantly lower percentages of pan T cells and CD8-positive cells (P < 0.02) compared with the HS group. L-EOP patients showed depressed IL-4 and TNF-alpha productivity compared with the HS group (P < 0.02). The EOP group showed significantly elevated antibody levels against Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola, and Fusobacterium nucleatum compared with the HS group (P < 0.05). The frequency with DQB1*0503 was significantly higher in the EOP patient group than the HS group (P = 0.045) due to the higher frequency in L-EOP patients than the HS group (P = 0.035). There were wide interindividual variations in each of the tests among patient and HS groups; however, EOP patients showed wider intradiagnostic group variations in certain host defensive cell functions than the other groups. There were some EOP patients who showed extremely low or high values in some tests; the EOP patients could be further divided into subgroups according to their host defensive and immunological profiles. However, there was heterogeneity in some of the other host immunological tests even in the subgroups.

CONCLUSIONS

The association of host immunological risk factors in EOP patients is widely varied and more complex than previously thought. These results indicate the difficulty of explaining the pathogenesis of EOP based on a single host risk factor and also emphasize the importance of critical assessment of not only EOP patient groups, but also individual patients.

Human equivalent of the mouse Nude/SCID phenotype: long-term evaluation of immunologic reconstitution after bone marrow transplantation

Human Nude/SCID (severe combined immunodeficiency) is the first severe combined immunodeficiency caused by mutation of the winged-helix-nude (WHN) gene, which is expressed in the thymus but not in the hematopoietic lineage. The disease is characterized by a T-cell defect, congenital alopecia, and nail dystrophy. A Nude/SCID patient who underwent bone marrow transplantation from the human leukocyte antigen-identical heterozygote brother was studied to investigate, in this unique model, the role of the thymus in immunologic reconstitution. Despite an increase in CD3(+), CD4(+), and CD8(+) cells, CD4(+) CD45 RA naive lymphocytes were not regenerated. Conversely, naive CD8(+) cells were normal. After an initial recovery, lymphocyte proliferation to mitogens progressively declined compared with controls and genotypically identical donor cells grown in the WHN(+/-) environment. Analysis of the T-cell receptor (TCR) repertoire of CD4(+) cells revealed that only 3 of 18 Vbeta families had an altered CDR3 heterogeneity length profile. Conversely, CD8(+) lymphocytes showed an abnormal distribution in most Vbeta families. These data indicate that the thymus is differentially required in the reconstitution of CD4(+) and CD8(+) naive subsets and in the maintenance of their TCR repertoire complexity. Taken together, these findings suggest that bone marrow transplantation is ineffective in the long-term cure of this form of SCID.

A novel syndrome of variant leukocyte adhesion deficiency involving defects in adhesion mediated by beta1 and beta2 integrins

Leukocyte adhesion deficiency type I (LAD-1) is a disorder associated with severe and recurrent bacterial infections, impaired extravascular targeting and accumulation of myeloid leukocytes, altered wound healing, and significant morbidity that is caused by absent or greatly diminished surface expression of integrins of the beta2 class. We report clinical features and analysis of functions of cells from a patient with a myelodysplastic syndrome and infectious complications similar to those in the severe form of LAD-1, but whose circulating neutrophils displayed normal levels of beta2 integrins. Analysis of adhesion of these cells to immobilized ligands and to endothelial cells and assays of cell-cell aggregation and chemotaxis demonstrated a profound defect in adhesion mediated by beta2 integrins indicative of a variant form of LAD-1. A novel cell line established from Epstein-Barr virus-transformed lymphoblasts from the subject demonstrated deficient beta2 integrin-dependent adhesive function similar to that of the primary leukocytes. In addition, these cells had markedly impaired beta1 integrin-dependent adhesion. Sequence analysis and electrophoretic mobility of beta1 and beta2 proteins from the cell line demonstrated that the defects were not a result of structural abnormalities in the integrin subunit chains themselves and suggest that the adhesive phenotype of these cells is due to one or more abnormalities of inside-out signaling mechanisms that regulate the activity of integrins of these classes. These features define a unique LAD-1 variant syndrome that may reveal important insights that are generally relevant to inside-out signaling of integrins, a molecular process that is as yet incompletely understood.

A novel CD18 genomic deletion in a patient with severe leucocyte adhesion deficiency: a possible CD2/lymphocyte function-associated antigen-1 functional association in humans

Leucocyte adhesion deficiency (LAD) is an autosomal-recessive genetic disease that is characterized clinically by severe bacterial infections and caused by mutations in the CD18 gene that codes for the beta2 integrin subunit. A patient with a severe LAD phenotype was studied and the molecular basis of the disease was identified as a single homozygous defect in a Herpes virus saimiri (HVS)-transformed T-cell line. The defect identified involves a deletion of 171 bp in the cDNA that encodes part of the proteic extracellular domain. This genetic abnormality was further studied at the genomic DNA level and found to consist of a deletion of 169 bp (from -37 of intron 4 to +132 of exon 5), which abolishes the normal splicing and results in the total skipping of exon 5. The 171-bp shortened 'in-frame' mRNA not only resulted in the absence of CD18 expression on the cell surface but also in its absence in the cytoplasm of HVS T-cell lines. Functionally, the LAD-derived HVS T-cell lines showed a severe, selective T-cell activation impairment in the CD2 (but not in the CD3) pathway. This defect was not reversible when exogenous interleukin-2 (IL-2) was added, suggesting that there is also a functional interaction of the lymphocyte function-associated antigen-1 (LFA-1) protein in the CD2 signal transduction pathway in human T cells, as has been previously reported in mice and in the human Papillon-Lefèvre syndrome. Thus, HVS transformation is not only a suitable model for T-cell immunodeficiency studies and characterization, but is also a good system for investigating the immune system in pathological conditions. It may also be used in the future in cellular models for in vitro gene-therapy trials.

Immunological study on CD3 defective cutaneous T cell lymphoma cells from a patient with Sézary syndrome

Here we investigated the nature of cutaneous T cell lymphoma (CTCL) cells lacking surface CD3. A large number of CD3- CD4 T cells were found in the peripheral blood and lesional skin of a patient with Sézary syndrome, which is a variant of CTCL. Southern blot analysis revealed that a clonal rearrangement of T cell receptor (TCR) genes was detected in the separated CD3- CD4 cells, whereas CD3+ CD4 cells showed no clonal rearrangement, indicating that the CD3- CD4 cells represented CTCL cells. However, the CTCL cells expressed TCR with a particular Vbeta apart from CD3. The CTCL cells showed significant responses to staphylococcal enterotoxins (SEs) in vitro, although they hardly responded to phytohaemagglutinin, Mycobacterium tuberculosis antigen, and alloantigen. They required antigen-presenting cells (APC) to respond to SEB. Blocking analyses with MoAbs revealed that they recognized SEB through TCR depending on HLA-DR and intercellular adhesion molecule-1 (ICAM-1). Taken collectively, these results indicate that the CTCL cells lacking surface CD3 could proliferate in response to bacterial superantigens, whereas the responses to conventional antigens were generally suppressed. These results also implied that CTCL could be exacerbated by bacterial infection.

Apoptosis as a mechanism of peripheral blood mononuclear cell death after measles and varicella-zoster virus infections in children

Viral infections may induce an acquired form of immunodeficiency, generally lasting a few weeks. In the more severe form, such as HIV infection, the immunodeficiency is permanent. Programmed death of T cells represents one of the mechanisms by which HIV determines the T cell functional impairment, finally resulting in the destruction of T cells. In this study, we evaluated whether an altered regulation of apoptosis was also implicated in the anergy associated with the common measles or varicella-zoster virus (VZV) infections in infancy. A spontaneous apoptosis of peripheral blood mononuclear cells was observed in children who had suffered from these infections as long as 6 mo after the acute disease. Apoptosis was demonstrated through analysis of cellular DNA content, morphologic evidence of cell nuclei shrinkage, and by analysis of DNA degradation. Stimulation of T cells through anti-CD4 MAb increased the number of apoptotic cells with a maximal effect 72 h after the stimulation. Our results suggest that apoptosis may account for the anergy that follows acute viral infections in infancy.

Simultaneous detection of DNA synthesis and cytokine production in staphylococcal enterotoxin B activated CD4+ T lymphocytes by flow cytometry

Assessment of T cell activation has traditionally been performed by measuring proliferation as a function of 3[H]-thymidine incorporation, or secretion of cytokines from activated peripheral blood mononuclear cells (PBMC) in culture. An alternative method for detection of proliferation at the single cell level utilizes incorporation of bromodeoxyuridine (BrdU), an analog of thymidine, into cellular DNA. After appropriate fixation and permeabilization of the cells, a monoclonal antibody (mAb) against BrdU conjugated with a fluorescent dye is employed to measure by flow cytometry the incorporated BrdU. Here, we report a flow cytometric procedure which can be used for the simultaneous detection of BrdU incorporation, activation markers such as CD69 and CD25, and intracellular cytokines in T cell subsets from activated PBMC. Our observations are consistent with the proposal that cytokine synthesis and cell proliferation occur sequentially in CD4+ T cells stimulated with the superantigen staphylococcal enterotoxin B (SEB). The majority of cells expressing the cytokines IFN-gamma and IL-2 at 48 h appear to have undergone DNA synthesis, however all proliferating cells do not express IFN-gamma or IL-2. The methods presented in this report offer a unique approach for studying simultaneous expression of key cellular activation events in phenotypically resolved lymphocyte populations.

Construction of retroviral vectors carrying human CD3 gamma cDNA and reconstitution of CD3 gamma expression and T cell receptor surface expression and function in a CD3 gamma-deficient mutant T cell line

CD3 gamma, a subunit of the T cell receptor-CD3 (TCR/CD3) complex, helps to support surface TCR/CD3 expression and participates in signal transduction for gene induction after antigen recognition by T lymphocytes, and in TCR/CD3 down-modulation. Humans with primary immunodeficiencies caused by inherited mutations in the CD3 gamma gene or in the gene encoding epsilon CD3é, another subunit of TCR/CD3 complex, have been previously reported. To develop a gene therapy protocol for CD3-deficient patients, CD3 gamma cDNA was orientationally inserted into two retroviral vectors (LNCX and LXSN), which resulted in recombinant vectors LNCG and LGSN, respectively. Two vector producer cell lines Am12/LNCG and Am12/LGSN were established from packaging cells GP+envAm12. Their mean viral titers were 6.5 x 10(6) and 2.0 x 10(7) cfu/ml, respectively, as shown by an improved retroviral vector production and transduction method that increases titers around five-fold over conventional methods. The presence of helper virus in vector stocks was tested by marker rescue assay and found to be < 1 cfu/ml. Southern blot analysis showed that multiple copies of the vectors were present in the genome of high-titer producers and that both vectors could transfer CD3 gamma cDNA into the genome of 3T3 cells. The vectors were used to correct in vitro a CD3 gamma-deficient Jurkat mutant cell line lacking TCR/CD3 expression and termed JGN (for Jurkat gamma negative). Both vectors increased TCR/CD3 expression in JGN (normally 2% using WT31 monoclonal antibody) to 34% and 37%, respectively, in G418-selected 3-week bulk cultures. Two clones from transduced JGN cells termed JGN/LNCG13 and JGN/LNCG15, with high TCR/CD3 expression (88% and 79%, respectively), were selected for further analyses. First, CD3 gamma protein reconstitution was demonstrated by immunoprecipitation. Second, interleukin-2 production after TCR/CD3 engagement and TCR/CD3 down-modulation in response to phorbol myristate acetate were shown to be comparable to wild-type Jurkat cells. We conclude that LNCG and LGSN may be useful for gene therapy purposes.

Stimulatory roles of muscarinic acetylcholine receptors on T cell antigen receptor/CD3 complex-mediated interleukin-2 production in human peripheral blood lymphocytes

It is known that there are some bidirectional interactions between the nervous and the immune systems via neurotransmitters and cytokines. To clarify whether any neurotransmitters modulate lymphocyte functions, we examined the effects of oxotremorine-M (Oxo-M) on interleukin-2 (IL-2) production in human peripheral blood lymphocytes by using enzyme-linked immunosorbent assays, Northern blot analyses, reverse transcriptase-polymerase chain reaction, and fluorescence-activated cell sorter. Pretreatment of cells with Oxo-M (10 nM to 10 microM) for 4-24 hr enhanced phytohemagglutinin (PHA)-induced IL-2 mRNA expression and markedly increased IL-2 production compared with those induced by PHA alone. Oxo-M alone did not affect IL-2 mRNA expression and IL-2 production. In CD3-positive T cells, pretreatment with Oxo-M for 24 hr enhanced PHA-induced IL-2 production. Furthermore, pretreatment with Oxo-M enhanced PHA-induced mRNA expression of the alpha and beta subunits of IL-2 receptors and DNA synthesis. Cytometric analysis showed Oxo-M treatment did not up-regulate expression of cell surface molecules such as CD3, CD2, CD4, CD8, and IL-2 receptors. These results suggest that activation of muscarinic receptors enhances T cell antigen receptor/CD3-induced IL-2 production.

T cells from individuals in advanced stages of HIV-1 infection do not proliferate but express activation antigens in response to HIV-1-specific antigens

Like T cells from healthy subjects, those of HIV-1-infected patients are capable of expressing activation antigens on their surface after antigenic or mitogenic stimulation, but their proliferative activity is strongly reduced or even absent, especially in patients with advanced stages of the disease. The characteristic of expressing activation antigens in response to different stimuli in the absence of cell proliferation is shared by CD4+ and CD8+ T-cell subsets from HIV-1-infected patients. The number of T cells capable of expressing CD25 and CD71 in response to HIV-1-related antigens but not of proliferating increased significantly with the progression of the disease, but the number of T cells capable of expressing the two activation antigens in response to the classic tetanus toxoid recall antigen decreased. The higher numbers of T cells capable of responding to HIV-1-related antigens in conjunction with a reduction in the number of T cells responding to recall antigens may explain the occurrence of different infections, including opportunistic microorganisms, during the more advanced stages of HIV-1 infection. Because the increase in the number of HIV-1 antigen-responding T cells (defined by CD25 and CD71 activation antigen expression) is a characteristic of symptomatic HIV-1-infected patients, expression (by flow cytometry) of these activation antigens on T cells in response to HIV-1 antigens could be used as a new marker of disease progression.

Heat-killed Bacillus subtilis inhibits T-cell proliferative response to mitogens and recall antigens

Heat-killed vegetative forms of Bacillus subtilis were found to impair considerably the capacity of human T-lymphocytes to secrete interleukin-2 (IL-2) and to proliferate (in terms of [3H]thymidine incorporation) after phytohaemagglutinin (PHA) stimulation. B. subtilis was also found to interfere with T-cell proliferation induced by concanavalin A (Con A) and the recall antigen tetanus toxoid (TT). The suppressive activity was dependent on bacterial concentration, and was not ascribed to mitogen, medium-nutrient absorption or cell killing. Moreover, B. subtilis did not interfere with mitogen-induced IL-2 receptor expression on the T-cell surface. On the other hand, B. subtilis did not interfere with T-cell proliferation induced by phorbol myristate acetate (PMA) and ionomycin stimulation. All data obtained suggest the binding of B. subtilis subcomponents to- or very close to-the T-cell receptor (TCR). Identification and purification of the basic structure(s) or component(s) of B. subtilis with TCR antagonist activity in vitro will help to exploit different aspects of T-cell activity and development, and possibly, will provide a means of specific control or modification of the immune response.

Herpes virus saimiri transformation of T cells in CD3 gamma immunodeficiency: phenotypic and functional characterization

The characterization of T cell immunodeficiencies could in part be supported by using stable cell lines in which biochemical and molecular studies of the defect could be carried out thereby omitting frequent bleeding of patients. First attempts to obtain such cell lines included HTLV-I transformation and exogenous IL-2 administration, but both models have important disadvantages. Recently, a virus isolated from the squirrel monkey, Herpes virus saimiri (HVS), has been reported to have the ability to transform T cells. A stable IL-2-dependent HVS-transformed T cell line from a CD3 gamma deficient patient has been obtained; and this cell line displays both the phenotypic and the functional characteristics of the patient's lymphocytes. Moreover, the line down-modulates TCR/CD3 surface expression upon CD3 engagement, as do the patient's lymphocytes, showing that CD3 gamma and its phosphorylation are not necessary for TCR/CD3 internalization. In addition, the abnormal staining pattern of different anti-TCR/CD3 monoclonal antibodies is preserved in the HVS-patient line. Since HVS is capable of transforming CD3 gamma- T cells, the CD3 gamma chain does not seem to be involved in the HVS receptor process. The fact that it is not possible to obtain a CD8+ HVS line from the CD3 gamma- patient supports the existence of a functional anomaly in his scanty CD8+ peripheral lymphocytes. Thus, HVS transformation is a suitable model for T cell immunodeficiency studies and characterization. It may also be used in the future in cellular models for in vitro gene therapy trials.

Congenital Alopecia and nail dystrophy associated with severe functional T-cell immunodeficiency in two sibs

We report on two sisters affected by congenital alopecia, nail dystrophy, and a severe T-cell immunodeficiency, presumably inherited as an autosomal-recessive disorder. The T-cell defect was characterized by severe functional impairment, as shown by the lack of proliferative response and upregulation of activation markers following mitogen stimulation. The functional abnormality occurred in spite of the presence of phenotypically mature of the defect. This is the first observation reported on an ectodermal disorder, characterized by alopecia and nail dystrophy, observed at birth, in association with a primary immunodeficiency. The hypothesis that these two events may be casually related is discussed.

Rapid flow cytometric method for measuring lymphocyte subset activation

Standard in vitro methods for assessing T-cell activation have typically measured either the proliferative responses of peripheral blood mononuclear cell (PBMC) cultures to various provocative stimuli employing tritiated thymidine incorporation or the secretion of specific cytokines from activated cells. These bulk assay methods suffer the drawback of being lengthy assays, and, in addition, they do not provide information about functional responses of individual lymphocyte subsets. This report describes a three-color flow cytometric method for the rapid analysis (4 hours) of individual T-cell subsets in whole blood responding to various provocative stimuli, including pokeweed mitogen, the comitogenic monoclonal antibodies (mAbs) CD2/CD2R, the superantigen staphylococcal enterotoxin B (SEB), and the specific antigen Candida albicans. After 4 hours, CD69 expression in response to CD2/CD2R paralleled thymidine incorporation measured after 72 hours. Variations in the proportions of CD4+ and CD4- T cells expressing CD69 were observed with different stimuli. These observations demonstrate the potential of multiparameter flow cytometry for the investigation of functional responses of individual T-cell subsets to a variety of stimuli in whole blood.

Altered T lymphocyte signaling in rheumatoid arthritis

Synovial and peripheral blood T cells from patients with rheumatoid arthritis are functionally deficient. This may be secondary to their reduced cytokine (e.g. interleukin-2) synthesis. We have investigated the possibility of an alteration in pathways common to interleukin-2 production and proliferation in peripheral blood T cells from patients with active rheumatoid arthritis. Intracellular calcium levels ([Ca2+]i) were analyzed by flow cytometric methods in Indo1-loaded T cells. These were purified by negative selection from patients or age/sex-matched controls, and stimulated with phytohemagglutinin-P or anti-CD3. Rheumatoid [Ca2+]i responses to both stimuli were reduced (p < 0.005). Patient cell samples included a larger proportion of non-responding cells, but even in the responsive population the magnitude of the response in rheumatoid cells was impaired compared with those in normal cell samples (p < 0.0001) for both stimuli. Proliferation responses were also impaired (p < 0.005), and there was a positive correlation between the paired [Ca2+]i elevation and proliferative responses for both stimuli. CD2 and CD3 expression were normal, and the proportions of CD4, CD8 and CD45RO and CD45RA subsets were also unaffected by disease. Thus a signaling defect downstream of CD2 or CD3 surface molecules may contribute to functional deficiencies in rheumatoid T lymphocytes. This effect is not due to non-steroidal anti-inflammatory drugs which some patients were taking. We have demonstrated similar alterations in [Ca2+]i responses and proliferation in a smaller study of patients with inflammatory bowel disease, indicating that such changes might be present in other chronic inflammatory states.

Functional defect of T cells in autoimmune gastritis

The functional response and phenotypic characterisation of peripheral blood T cells were studied in 41 patients with autoimmune gastritis--nine patients with autoimmune gastritis alone, 11 with untreated pernicious anaemia, and 21 with resolved pernicious anaemia who were taking vitamin B-12. Phenotypic analysis showed no changes in the CD4/CD8 ratio in any group of patients. CD3+ cells were significantly decreased and CD16+ cells were significantly increased in patients with autoimmune gastritis alone. Phytohaemagglutinin induced T cell proliferation, with or without interleukin 2, was reduced in the three groups. T cell proliferation induced by phorbol myristate acetate was normal. Interleukin 2 production of phytohaemagglutinin-stimulated lymphocytes was normal in the three groups. Five patients with pernicious anaemia treated with vitamin B-12 were followed and persistent hypoproliferation of T cells in response to phytohaemagglutinin was observed. The follow up study of the phenotype of these patients showed a significant increase of the CD2+ CD3- lymphocyte population after six months' treatment. In conclusion, the three groups of autoimmune gastritis patients studied have a functional defect in T cells that is independent of B-12 treatment and of the presence of pernicious anaemia.

Peripheral blood reduction of memory (CD29+, CD45RO+, and "bright" CD2+ and LFA-1+) T lymphocytes in Papillon-Lefèvre syndrome

A Papillon-Lefèvre patient with characteristic chronic periodontal disease and palmoplantar keratoderma was studied over a 4-year period. An abnormal T-cell phenotype was steadily observed in peripheral blood; both low numbers of CD29+ and CD45RO+ cells and a low density surface expression of CD2 and LFA-1 molecules were found. T-cell activation through CD3, CD2 and ConA, PWM and IL-2 receptors was normal; however, there was impairment in the activation via CD28. CD2, LFA-1 and CD45 molecules were normal in charge and molecular weight. There was no tissue sequestering of T lymphocytes in periodontal lesions, but rather a relative T-cell reduction. It is suggested that an important decrease of the so-called "memory/hyperreactive" (CD45RO-positive) T cells does exist; therefore, hyperreactive T cells would not be available in sufficient numbers to leave the bloodstream through blood vessel endothelium, and the periodontium would be left without these important defenses and thus exposed to chronic infections. A disregulated factor affecting the transition from "naive" to "memory" T cells and the increase in certain surface molecules expression (i.e., CD2, LFA-1, CD29, and CD45RO) or the reversion from memory to naive T cells may be responsible for the disease pathogenesis. CD2 and LFA-1 molecule synthesis might be conjointly regulated on T lymphocytes.

Primary T lymphocyte immunodeficiency associated with a selective impairment of CD2, CD3, CD43 (but not CD28)-mediated signal transduction

A 2-year-old female with important signs of immune response failure against virus, bacteria, fungi and protozoa and no obvious humoral or lymphocyte phenotypical defect was studied. Both peripheral blood mononuclear cells and IL-2-dependent T cell lines derived from the patient showed a severe selective T cell activation impairment via CD2, CD3 and CD43; however, this defect was reversible with the addition of either IL-2, or phorbol myristate acetate (PMA) or anti-CD28 antibodies. Concordantly, the induction of IL-2 (and, in part, IL-3 and IL-4) messenger RNA was severely reduced in stimulated T cells, but that of other cytokines was either normal (IL-5) or only slightly diminished (interferon-gamma (IFN-gamma)). It is concluded that an activation T cell defect exists previous to protein kinase C (PKC) and between membrane receptors and the activation pathway of certain response genes encoding for interleukins involved in proliferation (i.e. IL-2, IL-3 and IL-4), but not of others (i.e. IL-5). The use of T cell lines from human T lymphocyte activation deficiencies allows dissection of T cell pathology and the corresponding physiological pathways. In the present description, there is an evident independence of the CD28 T cell activation pathway from those induced through CD2 or CD3, and the differential gene regulation of the different interleukins.

Adhesion molecules in lung diseases

The human body possesses highly specialized cellular defense mechanisms that, when activated pathologically, can induce a number of immunologic disorders. For a normal cellular immune response, the following conditions must be fulfilled: (1) accumulation of white blood cells, (2) their diapedesis through the vessel walls of the inflammatory area affected by an injurious agent, and (3) normal cellular effector functions in the tissue. This cascade of inflammatory processes has recently been shown to be regulated by a group of molecules that are termed adhesion molecules and consist of three subfamilies: selectins, the immunoglobulin supergene family, and integrins. The cellular functions influenced by adhesion molecules include, among others, cytotoxic T-cell responses, CD4-dependent activation of B lymphocytes by T lymphocytes, activation of granulocytes and macrophages, phagocytosis of opsonized particles by monocytes, macrophages, and granulocytes, antigen-presenting function of macrophages, their antibody-dependent cytotoxicity, initiation of a respiratory burst by white blood cells, and activation of fibroblasts. Studies performed in recent years have shown that pathogenetically relevant changes in the expression and function of adhesion molecules are involved in a variety of pulmonary diseases. These changes include the accumulation and activation of alveolar macrophages in smokers, experimentally induced bronchial hyperreactivity in bronchial asthma, accumulation of eosinophils in allergic rhinitis, bleomycin-induced pulmonary fibrosis, binding of viruses and bacteria to respiratory mucosa, and various mechanisms of acute damage to pulmonary parenchyma. Though their role in tumor development is still unclear, adhesion molecules are obviously involved in determining the route and organotropism of metastases. Further studies of the function of adhesion molecules in pulmonary diseases will contribute to our understanding of the pathomechanisms of these diseases and, through the development of specific antibodies, may provide attractive new therapeutic approaches to problems for which treatment is not yet available.

Selective impairment of T lymphocyte activation through the T cell receptor/CD3 complex after cytomegalovirus infection

Cytomegalovirus (CMV) infection is reported to cause transient immunosuppression in man. In this study we have analysed the effect of CMV on T lymphocyte function in 29 children diagnosed for acute CMV infection. Peripheral blood mononuclear cells (PBMC) obtained from the patients showed a significant specific impairment in their proliferative response to enterotoxins A and C1, to concanavalin A and to the anti-CD3 MoAb OKT3. The impaired responses were corrected with exogenous IL-2. In contrast, stimulation using phytohaemagglutinin, as well as activation signals delivered through the surface molecules CD26 or CD28, elicited normal proliferative responses in CMV PBMC. The results indicate that the T cell anergy associated with CMV infection is restricted to the T cell receptor/CD3 activation pathway.

From pathology to physiology of the human T-lymphocyte receptor

The recent description of a selective human CD3 gamma deficiency and other T-cell receptor (TCR)/CD3 structural and functional defects, together with previous biochemical data on the structure and interactions of the TCR/CD3 complex, may aid in elucidating the physiology of this multi-subunit membrane ensemble. CD3 gamma seemed to be required for the commitment and thymic maturation of an important fraction of T lymphocytes to the CD8 (but not CD4) lineage, perhaps by participating with the CD8 co-receptor in the instructive signal delivered through the alpha beta TCR during intrathymic positive selection by HLA class I molecules. The homologous CD3 delta component would, in contrast, be necessary for the selection of CD4 lymphocytes by HLA class II molecules. The interaction of CD4 and CD8 with the TCR/CD3 complex during antigen recognition may thus be asymmetrical, taking place through CD3 delta and gamma, respectively. Also, the existence of in vivo functional TCR/CD3 hemireceptors (lacking either CD3 gamma or CD3 delta) is suggested, and defects in their relative amount on the T-cell surface may disrupt unresponsiveness to self antigens and generate autoimmunity.