Adhesion receptors in lymphocyte activation

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

Function and Dynamics of Tetraspanins during Antigen Recognition and Immunological Synapse Formation

Tetraspanin-enriched microdomains (TEMs) are specialized membrane platforms driven by protein–protein interactions that integrate membrane receptors and adhesion molecules. Tetraspanins participate in antigen recognition and presentation by antigen-­presenting cells (APCs) through the organization of pattern-recognition receptors (PRRs) and their downstream-induced signaling, as well as the regulation of MHC-II–peptide trafficking. T lymphocyte activation is triggered upon specific recognition of antigens present on the APC surface during immunological synapse (IS) formation. This dynamic process is characterized by a defined spatial organization involving the compartmentalization of receptors and adhesion molecules in specialized membrane domains that are connected to the underlying cytoskeleton and signaling molecules. Tetraspanins contribute to the spatial organization and maturation of the IS by controlling receptor clustering and local accumulation of adhesion receptors and integrins, their downstream signaling, and linkage to the actin cytoskeleton. This review offers a perspective on the important role of TEMs in the regulation of antigen recognition and presentation and in the dynamics of IS architectural organization.

Interferon γ limits the effectiveness of melanoma peptide vaccines

The development of effective therapeutic vaccines to generate tumor-reactive cytotoxic T lymphocytes (CTLs) continues to be a top research priority. However, in spite of some promising results, there are no clear examples of vaccines that eradicate established tumors. Most vaccines are ineffective because they generate low numbers of CTLs and because numerous immunosuppressive factors abound in tumor-bearing hosts. We designed a peptide vaccine that produces large numbers of tumor-reactive CTLs in a mouse model of melanoma. Surprisingly, CTL tumor recognition and antitumor effects decreased in the presence of interferon γ (IFNγ), a cytokine that can provide therapeutic benefit. Tumors exposed to IFNγ evade CTLs by inducing large amounts of noncognate major histocompatibility complex class I molecules, which limit T-cell activation and effector function. Our results demonstrate that peptide vaccines can eradicate large, established tumors in circumstances under which the inhibitory activities of IFNγ are curtailed.

Comparative Analysis of Polymer and Linker Chemistries on the Efficacy of Immunocamouflage of Murine Leukocytes

Membrane grafting of methoxypoly(ethylene glycol) [mPEG] to allogeneic leukocytes attenuates allorecognition and significantly reduces the risk of graft-versus-host disease in mice. To optimize the immunological efficacy of polymer grafting, murine splenocytes were modified using three differing linker chemistries: CmPEG (5 kDa), BTCmPEG (5 and 20 kDa) and TmPEG (5 kDa). In vitro immunocamouflage efficacy was examined by flow cytometic analysis of leukocyte markers and mixed lymphocyte reactions (MLR). In contrast to CmPEG and BTCmPEG, TmPEG exerted significant cellular toxicity. Flow cytometric analysis demonstrated that both CmPEG and BTCmPEG were highly effective at camouflaging cell surface markers while TmPEG was ineffective. Furthermore, CmPEG and BTCmPEG dramatically blocked MLR allorecognition and cellular proliferation. Polymer length was the most critical factor in the immunocamouflage of cells with the BTCmPEG 20 kDa being the most effective. In contrast to other immunomodulatory approaches, immunocamouflage of leukocytes yields a multivalent effect globally interfering with attachment, allorecognition, presentation and costimulation pathways.

Lrrk2 and chronic inflammation are linked to pallido-ponto-nigral degeneration caused by the N279K tau mutation

Mutations in the leucine-rich repeat kinase 2 gene (LRRK2) have been identified in families with autosomal dominant late-onset Parkinson disease (PD). Lrrk2 is a phylogenetically conserved, ubiquitous protein, which is constitutively expressed in various cells including neurons and glial cells of human brain. We recently reported that Lrrk2 is identified in Lewy bodies in PD as well as in neuronal and glial inclusions in several other neurodegenerative disorders. Here we show that Lrrk2 is closely associated with the tau-positive inclusions in eight members of a family with frontotemporal dementia of the pallido-ponto-nigral degeneration type linked to the chromosome 17 N279K tau mutation (N279K/FTDP-17/PPND). Lrrk2 is colocalized with tau in oligodendroglial coiled bodies and intracytoplasmic neuronal inclusions. HLA-DR positive reactive microglia and ICAM-1 positive reactive astrocytes accumulated in affected areas demonstrating that inflammatory processes are also involved in the disease pathogenesis. Western blot analysis of soluble extracts of N279K/FTDP-17/PPND brain tissue suggests that C-terminal fragment(s) of apparent 64-75 kDa molecular weight may be the major Lrrk2 species in pathological deposits. The possibility that Lrrk2 is linked with various neurodegenerative disorders through the ubiquitin proteosome pathway is discussed. The results indicate that Lrrk2 is linked to frontotemporal atrophy of PPND type caused by N279K tau mutation. They also show that chronic inflammation is involved in the pathogenesis of N279K/FTDP-17/PPND.

A phase I/II randomized open-label multicenter trial of efalizumab, a humanized anti-CD11a, anti-LFA-1 in renal transplantation

Leukocyte function associated antigen-1 (LFA-1) has a multifaceted role in the immune response, including adhesion and trafficking of leukocytes, stabilizing the immune synapse of the MHC-TCR complex and providing costimulation signals. Monoclonal antibodies to the CD11a chain of LFA-1 have been seen to result in effective immunosuppression in experimental models. Efalizumab, a humanized IgG1 anti-CD11a, is approved for use in psoriasis and may provide effective immunosuppression in organ transplantation. Thirty-eight patients undergoing their first living donor or deceased renal transplant were randomized to receive efalizumab 0.5 or 2 mg/kg weekly subcutaneously for 12 weeks. Patients were maintained on full dose cyclosporine, mycophenolate mofetil and steroids or half dose cyclosporine, sirolimus and prednisone. At 6 months following transplant patient survival was 97% and graft survival was 95%. Clinical biopsy-proven acute rejection in the first 6 months after transplantation was confirmed in 4 of 38 patients (11%). Three patients (8%) developed post transplant lymphoproliferative disease, all treated with the higher dose efalizumab and full dose cyclosporine. The two doses of efalizumab resulted in comparable saturation and modulation of CD11a. This phase II trial suggests that efalizumab may warrant further investigation in transplantation.

Inflammation as a causative factor in the aetiology of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting mainly the elderly, although a small proportion of PD patients develop the illness at a much younger age. In the former group, idiopathic PD patients, the causes of the illness have been the subject of longstanding debate with environmental toxins, mitochondrial dysfunction, abnormal protein handling and oxidative stress being suggested. One problem has been that the epidemiology of PD has offered few clues to provide evidence for a single major causative factor. Comparatively recently it has been found that in both patients and experimental models of PD in animals neuroinflammation appears to be a ubiquitous finding. These cases present with all of the classical features of inflammation including phagocyte activation, increased synthesis and release of proinflammatory cytokines and complement activation. Although this process is vital for normal function and protection in both the CNS, as in the periphery, it is postulated that in the aetiology of PD this process may spiral out of control with over activation of microglia, over production of cytokines and other proinflammatory mediators as well as the release of destructive molecules such as reactive oxygen species. Given that dopaminergic neurons in the substantia nigra are relatively vulnerable to 'stress' and the region has a large population of microglia in comparison to other CNS structures, these events may easily trigger neurodegeneration. These factors are examined in this review along with a consideration of the possible use of anti-inflammatory drugs in PD.

Role of ICAM-1 in persisting inflammation in Parkinson disease and MPTP monkeys

It has been established that neuroinflammation is present in the substantia nigra (SN) of Parkinson disease (PD) cases but the factors responsible are as yet unknown. One contributing protein may be the intercellular adhesion molecule-1 (ICAM-1, CD54). ICAM-1 with its counter receptor, the lymphocyte function-associated antigen 1 (LFA-1) is known to play a key role in inflammatory processes and in T-cell mediated host defense mechanisms. We detected large numbers of ICAM-1-positive reactive astrocytes in the SN of a series of 14 patients with neuropathologically confirmed PD, including 3 of familial origin, compared with 11 age-matched controls. In PD SN, these ICAM-1-positive reactive astrocytes were particularly concentrated around many residual neurons in areas of heavy neuronal loss and extracellular melanin accumulation. LFA-1-positive reactive microglia gathered in areas of intense ICAM-1 expression, and LFA-1-positive leukocytes were identified infiltrating the tissue. Double immunostaining for ICAM-1 and LFA-1 revealed aggregates of reactive microglia embedded in areas of diffuse ICAM-1. Leukocyte counts were 5 fold higher in PD SN compared to controls (P < 0.001). Similar over-expression of ICAM-1 was found in monkeys that had been exposed to MPTP from 5.5 to 14 years previously compared with control monkeys. The presence of ICAM-1-positive reactive astrocytes in Parkinson disease and MPTP-treated monkeys is indicative of a sustained inflammatory process and suggests that antiinflammatory agents may have a place in PD therapy.

The CD2 family of natural killer cell receptors

The CD2 family of receptors is evolutionarily conserved and widely expressed on cells within the hematopoietic compartment. In recent years several new members have been identified with important roles in the immune system. CD2 family members regulate natural killer (NK) cell lytic activity and inflammatory cytokine production when engaged by ligands on tumor cells. Furthermore, a subfamily of CD2 receptors, the CD 150-like molecules, has been implicated in the pathogenesis of X-linked lymphoproliferative disease (XLP). Many of these receptors have now been shown to bind homophilically or heterophilically to other molecules within the family. With these discoveries a novel mechanism for lymphocyte regulation has emerged: CD2 family members on NK cells engage ligands on neighboring NK cells, leading to NK cell stimulation. Moreover, heterotypic stimulatory interactions between NK cells and other leukocytes also occur. In this manner, CD2 family members may provide interlymphocyte communication that maintains organization within the hematopoietic compartment and amplifies immune responses. This review discusses these multiple roles for CD2 family members, focusing specifically on the regulation of NK cells.

Cell adhesion molecules and extracellular matrix proteins: potential therapeutic applications

Adhesion plays a central role as a recognition system, guiding the interaction between individual cells, and thereby regulating many biological processes. Adhesion can occur via cell-cell or cell-extracellular matrix interactions through several major cell adhesion molecule (CAM) families, including selectins, integrins, immunoglobulins and cadherins. Recent studies have focused on the elucidation of adhesive ligands responsible for the different types of cellular adhesion. Significant breakthroughs in CAM research are a result of various developments, including the purification of various adhesive proteins from different tissue sources and cloned adhesion molecules, the generation of specific monoclonal antibodies, the development of functional assays and the identification of certain genetic disorders linked to CAM defects. This has led to an increased understanding of the importance of CAM as a key therapeutic target.

Mononuclear cell antigen expression after contact with one-day disposable contact lens materials

PURPOSE

To analyse the effects of 1-day disposable contact lens (CL) material on mononuclear cell activation antigens and adhesion molecules, in an in vitro model set up in order to simulate the first 2 h of wear.

METHODS

Etafilcon A and Hilafilcon A materials were analysed. Mononuclear cells, collected from peripheral blood samples of normal human donors, were placed in contact with the materials, both new and coated with artificial tear solution. As a control, Thermanox coverslips and a group with no material were included. Immunofluorescence reactions were carried out on cells, to study the distribution of activation (HLA-DR, CD25, CD69) and adhesion (CD11a, CD18, CD54) molecules; the flow cytometry technique was used to analyse cells.

RESULTS

Statistically significant results were demonstrated for the CD69 and all the 3 adhesion molecules. Artificial tear coating enhanced the mononuclear cell response.

CONCLUSIONS

The daily mononuclear cell activation can lead, with time, to production of inflammatory mediators that may be responsible for discomfort or, at worst, intolerance and definitely to CL wear remittance.

Regulation of inducible class II MHC, costimulatory molecules, and cytokine expression in TGF-beta1 knockout renal epithelial cells: effect of exogenous TGF-beta1

As reports of mice genetically deficient for TGF-beta1 demonstrated aberrant renal class II MHC expression, we investigated inducible class II MHC expression on renal tubular epithelial cells derived from TGF-beta1 knockout (-/-) and wild-type (+/+) mice. IFN-gamma markedly upregulated class II MHC (I-A(b)) expression in both (-/-) and (+/+) tubular epithelial cells. Coincubation studies of (+/+) and (-/-) tubular epithelial cells with IFN-gamma+LPS, or pretreatment of these cells with TGF-beta1, revealed inhibition of IFN-gamma-induced I-A(b) mRNA and cell surface expression that occurred via a decrease in class II transactivator gene expression in both (+/+) and (-/-) tubular epithelial cells. In addition, ICAM-1 was constitutively expressed on both (+/+) and (-/-) tubular epithelial cells and was upregulated by IFN-gamma or IFN-gamma+LPS. ICAM-1 expression in (+/+) and (-/-) tubular epithelial cells, however, was decreased by TGF-beta1. Parallel analysis evaluating B7-1 expression detected low levels of B7-1 in unstimulated (+/+) and (-/-) tubular epithelial cells that were increased by IFN-gamma, LPS, and IFN-gamma+LPS. IFN-gamma+LPS-mediated upregulation of B7-1 was also blocked by pretreatment with TGF-beta1. Cytokine analysis detected significantly higher levels of TNF-alpha and MIP-1alpha mRNA in all treated (-/-) preparations than in (+/+) tubular epithelial cell controls. These studies demonstrate normal patterns of class II MHC, ICAM-1, and B7 expression in TGF-beta1 (-/-) tubular epithelial cells in response to IFN-gamma, LPS, and TGF-beta1. Upregulated cytokine expression at baseline and in response to proinflammatory mediators is apparent in (-/-) tubular epithelial cells, however, and suggests that dysregulation of cytokine expression in inflammatory responses may be a primary event in multifocal inflammation observed in TGF-beta1-deficient animals.

Differential recruitment of alpha2beta1 and alpha4beta1 integrins to lipid rafts in Jurkat T lymphocytes exposed to collagen type IV and fibronectin

Collagen type IV (CnIV) and fibronectin (Fn) were used as ligands to study the distribution of alpha(2)beta(1) and alpha(4)beta(1) integrins in low-density, detergent-resistant microdomains (DRM) of Jurkat lymphocytes. CnIV-coated microspheres induced (optical trapping) the redistribution of GM(1)-associated fluorescence from the cell periphery to the area of contact. This was not observed in cells treated with beta-methyl cyclodextrin (MCD). Fn- or bovine serum albumin-coated microspheres did not modify the peripheral distribution of fluorescence. These observations were confirmed by confocal microscopy. Western blot analysis of cells exposed to surfaces coated with CnIV revealed that the alpha(2)-subunit was initially present at low levels in DRM, became strongly associated after 40 min, and returned to basal levels after 75 min. Fn induced a slight recruitment of the beta(1)-integrin alpha(4)-subunit in DRM after 5 and 10 min, followed by a return to basal levels. Neither CnIV nor Fn triggered significant changes in the distribution of the beta(1)-subunit in DRM. Fn- and CnIV-coated microspheres or surfaces coated with these ligands triggered a MCD-sensitive mobilization of Ca(2)(+). MCD did not alter the state of the Ca(2)(+) reserves. The differential distributions of the alpha(2)beta(1) and alpha(4)beta(1) integrins in DRM may provide one additional step in the regulation of outside-in signaling involving these integrins.

Antioxidant regulation of cell adhesion

Cell-cell and cell-matrix contacts are dependent on cell surface density, localization, and avidity state of surface-localized adhesion molecules. Cell adhesion represents a process that is centrally important in immune function and inflammation. This process is sensitive to various agonists including oxidants. Oxidants may directly as well as indirectly induce cell adhesion. In other cases, cytokines and related agents may induce cell adhesion by oxidant-dependent mechanisms. Various redox-sensitive sites in the signal transduction path leading to cell adhesion have been identified. Different chemical classes of nutritional antioxidants regulate cell adhesion by modulating specific signal transduction pathways. Numerous studies have confirmed that physical exercise influences the redox status of various cells and tissues. Recent evidences also show that physical exercise influences several cell adhesion related molecules. Whether such regulation has a redox component remains to be tested. Antioxidant supplementation studies testing the effect of exercise on cell adhesion should provide critical insight.

Determination of the relationship between T cell responsiveness and the number of MHC-peptide complexes using specific monoclonal antibodies

We describe the generation of three mAbs that recognize the complex of the class II MHC molecule IEk bound to a peptide derived from the carboxyl terminus of moth cytochrome c (residues 95-103). Reactivities of these mAbs are sensitive to single alterations in the sequence of both helices of the MHC molecule and to the bound peptide. The epitopes of these reagents are distinct but overlap substantially. One of these mAbs specifically blocks lymphokine release by T cells responsive to this complex but not others. We have used another to examine how the number of complexes on an APC is related to its ability to stimulate T cells. We find that 200-400 complexes per cell are necessary and sufficient to induce a degree of stimulation, whereas maximum stimulation is achieved only if more than 5000 complexes are present. The analysis indicates that T cell activation is a stochastic process.

Molecular mechanisms of T lymphocyte activation: convergence of T cell antigen receptor and IL-1 receptor-induced signaling at the level of IL-2 gene transcription

Co-stimulation of murine EL-4 thymoma cells-carrying high numbers of TCR and type I IL-1 receptors (IL-1R)-with anti-CD3 antibodies and IL-1 resulted in synergistic enhancement of IL-2 synthesis. While the extracellular signal-regulated kinase (ERK) cascade was activated by both receptors, IL-1 preferentially stimulated Jun-N-terminal kinases (JNK) and p38 mitogen-activated kinase or microtubule-associated protein kinase (MAPK). Interruption of TCR- or IL-1R-stimulated ERK cascade by PD-98059, a specific inhibitor of MAP/ERK kinase (MEK), resulted in partial suppression of nuclear factor of activated T cells activation and in complete inhibition of IL-1-stimulated NFkappaB activation. Suppression of activation of both MEK and p38 MAPK resulted in significant inhibition of IL-2 gene expression. The results show that maximal activation of the IL-2 gene requires activation of at least two different protein kinase cascades, i.e. of the ERK and p38 pathways but presumably also that of JNK which converge at the level of the IL-2 promoter resulting in enhancement of its transcriptional activity.

Presence of activated lymphocytes in the peripheral blood of patients with halo nevi

BACKGROUND

The involution of the central pigmented lesion in halo nevus (HN) seems to be mediated by an immune response against self antigens expressed by melanocytes.

OBJECTIVE

We assessed the presence of activated lymphocytes in the peripheral blood lymphocytes from patients with HN.

METHODS

Peripheral blood was obtained from patients with HN associated with benign pigmented lesions (5) or melanoma (2) as well as from patients with melanoma without HN (5) and healthy subjects (10). Activated lymphocytes were detected by flow cytometry analysis using monoclonal antibodies (mAb) against CD69, CD71, CD98, HLA-DR, and activated beta(1) integrins (HUTS-21 mAb).

RESULTS

The peripheral blood lymphocytes from patients with HN, associated with either benign or malignant lesions, exhibited a significantly higher expression of all activation markers studied compared with patients with melanoma without HN or compared with healthy subjects. Therefore the peripheral blood of HN patients contained a significant fraction of lymphocytes with an activated (CD69(+), HLA-DR(+), CD98(bright)), cell proliferating (CD71( bright)), and high adhesive (HUTS-21(bright)) phenotype. These activated cells disappeared from peripheral blood after the surgical resection of the skin lesion.

CONCLUSION

Our findings further support the involvement of immune activation in HN phenomenon.

The Nonintegrin Laminin Binding Protein (p67 LBP) Is Expressed on a Subset of Activated Human T Lymphocytes and, Together with the Integrin Very Late Activation Antigen-6, Mediates Avid Cellular Adherence to Laminin

A search for genes expressed in activated T cells revealed that the nonintegrin, 67-kDa laminin binding protein (p67 LBP) is expressed on the surface of a subset (10–15%) of activated peripheral blood T cells. Surface p67 LBP expression is detectable by FACS using the anti-p67 LBP mAb, MLuC5, within 6 h of T cell activation with phorbol dibutyrate and ionomycin, peaks 18–36 h postactivation, and persists for 7–10 days. The subset of T cells expressing p67 LBP is composed of mature, single-positive cells (85% CD4+8−, 15% CD4−8+) of memory cell phenotype (100% CD45 RO+/CD45 RA−). The p67 LBP+ T cells also express the integrin α6 chain (CD49f), which is known to associate with p67 LBP on tumor cells. In addition, the p67 LBP+ T cells express the integrin β1, which associates with α6 in the laminin-specific integrin receptor very late activation Ag (VLA)-6 (α6β1). Expression of an exogenous cDNA encoding the 37-kDa LBP precursor (p37 LBPP) confers p67 LBP surface expression on a p67 LBP-negative Jurkat T cell line (B2.7). Expression of p67 LBP induces B2.7 transfectants to adhere to laminin, but avid laminin binding depends on coexpression of VLA-6. Taken together, these data indicate that p67 LBP is an activation-induced surface structure on memory T cells that, together with VLA-6, mediates cellular adherence to laminin.

Stealth Cells: Prevention of Major Histocompatibility Complex Class II-Mediated T-Cell Activation by Cell Surface Modification

Transfusion or transplantation of T lymphocytes into an allogeneic recipient can evoke potent immune responses including, in immunocompromised patients, graft-versus-host disease (GVHD). As our previous studies demonstrated attenuated immunorecognition of red blood cells covalently modified with methoxy(polyethylene glycol) (mPEG), we hypothesized that T-cell activation by foreign antigens might similarly be prevented by mPEG modification. Mixed lymphocyte reactions (MLR) using peripheral blood mononuclear cells (PBMC) from HLA class II disparate donors demonstrate that mPEG modification of PBMC effectively inhibits T-cell proliferation (measured by 3H-thymidine incorporation) in a dose-dependent manner. Even slight derivatization (0.4 mmol/L mPEG per 4 × 106 cells) resulted in a ≥75% decrease, while higher concentrations caused ≥96% decrease in proliferation. Loss of PBMC proliferation was not due to either mPEG-induced cytotoxicity, as viability was normal, or cellular anergy, as phytohemagglutinin (PHA)-stimulated mPEG-PBMC demonstrated normal proliferative responses. Addition of exogenous interleukin (IL)-2 also had no proliferative effect, suggesting that the mPEG-modified T cells were not antigen primed. Flow cytometric analysis demonstrates that mPEG-modification dramatically decreases antibody recognition of multiple molecules involved in essential cell:cell interactions, including both T-cell molecules (CD2, CD3, CD4, CD8, CD28, CD11a, CD62L) and antigen-presenting cell (APC) molecules (CD80, CD58, CD62L) likely preventing the initial adhesion and costimulatory events necessary for immune recognition and response.

Stealth Cells: Prevention of Major Histocompatibility Complex Class II-Mediated T-Cell Activation by Cell Surface Modification

Transfusion or transplantation of T lymphocytes into an allogeneic recipient can evoke potent immune responses including, in immunocompromised patients, graft-versus-host disease (GVHD). As our previous studies demonstrated attenuated immunorecognition of red blood cells covalently modified with methoxy(polyethylene glycol) (mPEG), we hypothesized that T-cell activation by foreign antigens might similarly be prevented by mPEG modification. Mixed lymphocyte reactions (MLR) using peripheral blood mononuclear cells (PBMC) from HLA class II disparate donors demonstrate that mPEG modification of PBMC effectively inhibits T-cell proliferation (measured by 3H-thymidine incorporation) in a dose-dependent manner. Even slight derivatization (0.4 mmol/L mPEG per 4 × 106 cells) resulted in a ≥75% decrease, while higher concentrations caused ≥96% decrease in proliferation. Loss of PBMC proliferation was not due to either mPEG-induced cytotoxicity, as viability was normal, or cellular anergy, as phytohemagglutinin (PHA)-stimulated mPEG-PBMC demonstrated normal proliferative responses. Addition of exogenous interleukin (IL)-2 also had no proliferative effect, suggesting that the mPEG-modified T cells were not antigen primed. Flow cytometric analysis demonstrates that mPEG-modification dramatically decreases antibody recognition of multiple molecules involved in essential cell:cell interactions, including both T-cell molecules (CD2, CD3, CD4, CD8, CD28, CD11a, CD62L) and antigen-presenting cell (APC) molecules (CD80, CD58, CD62L) likely preventing the initial adhesion and costimulatory events necessary for immune recognition and response.

TGF-beta1 down-regulates induced expression of both class II MHC and B7-1 on primary murine renal tubular epithelial cells

BACKGROUND

We examined the immunomodulatory effects of transforming growth factor-beta1 (TGF-beta1) on the regulation of class II MHC and costimulatory molecule expression in a primary renal tubular epithelial cell line, called F1K.

METHODS

Class II major histocompatibility complex (MHC), class II transactivator, B7-1, intercellular adhesion molecule-1 (ICAM-1) and interferon-gamma (IFN-gamma) receptor beta chain were evaluated in untreated and cytokine-treated F1K by Northern hybridization analysis and flow cytometry. T cell activation studies were performed to assess TGF-beta1-mediated effects on antigen presenting cell function of F1K.

RESULTS

Pretreatment of F1K with TGF-beta1 markedly inhibited IFN-gamma-induced class II MHC expression, by both FACS and Northern analysis. Total class II transactivator mRNA levels were also diminished by TGF-beta1, indicating that class II MHC modulation in F1K results from inhibition of this intermediate protein. As previous studies demonstrated that cotreatment of F1K cells with IFN-gamma + lipopolysaccharide (LPS) induces B7-1, we evaluated the potential regulatory effects of TGF-beta1 exposure on B7-1 expression. Our studies revealed that B7-1 mRNA and cell-surface expression in IFN-gamma + LPS-treated F1K were decreased by TGF-beta1 pretreatment. Functional studies evaluating TGF-beta1-mediated effects were performed with IFN-gamma + LPS-treated F1K and MR1.3, a nephritogenic CD4+ Th2 clone derived from kidneys of animals with autoimmune glomerulonephritis. Interleukin (IL)-4 production assays demonstrated activation of MR1. 3 by IFN-gamma + LPS-treated cells, but not by IFN-gamma + LPS-treated cells previously exposed to TGF-beta1, indicating that TGF-beta1-mediated inhibition of class II MHC and B7-1 expression alters the antigen presenting cell function of F1K.

CONCLUSIONS

These studies describe the proscriptive influence of TGF-beta1 on class II MHC and B7-1 expression in renal tubular epithelial cells. Such findings indicate that TGF-beta1 alters the antigen presenting cell function of renal tubular epithelial cells in vitro, and suggest a potential mechanism for immunosuppression of T cell-mediated renal immune responses in vivo.

IFN-gamma and LPS differentially modulate class II MHC and B7-1 expression on murine renal tubular epithelial cells

BACKGROUND

We have investigated inducible class II major histocompatibility complex (MHC) and B7 expression on primary murine renal tubular epithelial cells, called F1K cells, and examined their role in activating nephritogenic T cells derived from kidneys of animals with autoimmune glomerulonephritis.

METHODS

Class II MHC, class II transactivator, and costimulatory molecule expression were evaluated in untreated and cytokine-treated F1K cells by Northern hybridization and flow cytometry. Cell-surface B7-1 expression was evaluated in vitro by immunoprecipitation and in vivo by immunohistochemistry. T-cell activation studies were then performed to assess the functional significance of B7-1 expression on F1K cells.

RESULTS

Coincubation of F1K cells with interferon (IFN)-gamma and lipopolysaccharide (LPS) significantly decreased IFN-gamma-induced class II MHC expression, by both fluorescence-activated cell sorting and Northern analyses. LPS-mediated inhibition of class II MHC in this setting was effected through a decrease in class II transactivator mRNA levels in treated F1K cells. By contrast, IFN-gamma and LPS coincubation induced B7-1 but not B7-2 expression in F1K cells, as detected by Northern analysis, flow cytometry, and immunoprecipitation. In addition, renal tubular staining for B7-1 was apparent in kidneys isolated from IFN-gamma+LPS-treated recipient mice, as well as mice with autoimmune glomerulonephritis. Further studies evaluated the interaction of F1K cells and MR1.3, a nephritogenic CD4+ Th2 clone derived from kidneys of animals with autoimmune glomerulonephritis. Cytokine production assays revealed that F1K cells activated MR1.3 cells if they were pretreated with both IFN-gamma and LPS 48 hours prior to exposure to nephritogenic T cells.

CONCLUSIONS

These studies are the first description of a differential regulation of class II MHC and B7-1 expression in renal tubular epithelial cells mediated by IFN-gamma and LPS. Such findings indicate that discrete proinflammatory stimuli could potentiate antigen-presenting capabilities of renal tubular epithelial cells in vivo and further suggest a direct role of such nonprofessional antigen-presenting cells in modulating renal immune responses.

Effects of space flight on surface marker expression

Space flight has been shown to affect expression of several cell surface markers. These markers play important roles in regulation of immune responses, including CD4 and CD8. The studies have involved flight of experimental animals and humans followed by analysis of tissue samples (blood in humans, rats and monkeys, spleen, thymus, lymph nodes and bone marrow in rodents). The degree and direction of the changes induced by space flight have been determined by the conditions of the flight. Also, there may be compartmentalization of the response of surface markers to space flight, with differences in the response of cells isolated from blood and local immune tissue. The same type of compartmentalization was also observed with cell adhesion molecules (integrins). In this case, the expression of integrins from lymph node cells differed from that of splenocytes isolated from rats immediately after space flight. Cell culture studies have indicated that there may be an inhibition in conversion of a precursor cell line to cells exhibiting mature macrophage characteristics after space flight, however, these experiments were limited as a result of technical difficulties. In general, it is clear that space flight results in alterations of cell surface markers. The biological significance of these changes remains to be established.

Signaling through the tetraspanin CD82 triggers its association with the cytoskeleton leading to sustained morphological changes and T cell activation

In this report, we provide new evidence of a crosstalk between T cell activation and adhesion processes through a functional cytokeleton. We show that CD82 signaling induces long-lasting adhesion, spreading and development of membrane extensions, involving actin polymerization. Addition of various co-stimuli (phorbol 12-myristate 13-acetate or monoclonal antibodies to CD3 or CD2) increases the CD82-induced morphological alterations and, reciprocally, CD82 engagement synergizes with these stimuli to induce T cell activation as indicated by both primary tyrosine phosphorylation and IL-2 production. Different kinases are involved in both processes. CD82 co-signaling involves src kinases including p56 Ick. On the other hand, the CD82-induced alterations of cell morphology are negatively regulated by cAMP-dependent kinases independently of activation of src kinases. Simultaneously with cytoskeletal rearrangements, we observed an inducible association of CD82 with the cytoskeletal matrix. In addition, the potentiating and stabilizing effects induced by CD82 cross-linking on tyrosine phosphorylation were abolished by cytoskeleton-disrupting agents. These results suggest that the actin polymerization triggered by CD82, through its ability to associate with the cytoskeletal matrix, is the primary step involved in the CD82 induced co-stimulatory activity. Our data provide further evidence for a direct role of the actin cytoskeleton as a major component for sustained signal transduction in T cells and suggest that tetraspanins could be "membrane organizers" connecting both surface and intracellular molecules.

Adhesion and signaling mediated by the cytoplasmic tails of leucocyte integrins

Integrins not only mediate cell adhesion but also contribute to a variety of other cellular processes including proliferation, cytokine production, cytotoxicity and apoptosis. They act as bi-directional signal transducers, mediating signaling from inside-to-outside the cell and from outside-to-inside the cell. Evidence is emerging that signaling through leukocyte integrins (beta 2 and beta 7) is distinct from signaling by the more widely distributed beta 1 integrins. Here we discuss the role of the cytoplasmic domains of leukocyte integrins and that of cytosolic proteins that bind integrins in mediating signal transduction. Distinct sites in the alpha as well as the common beta chain contribute to this process. We also show that beta 2 integrin distribution on the cell surface is of particular relevance for leukocytes to rapidly alter their adhesive state and display their highly dynamic adhesive behavior. From these and recently published findings the picture is arising that particular cell functions may be supported by integrin-specific signaling pathways.

Chimeric scFv/gamma receptor-mediated T-cell lysis of tumor cells is coregulated by adhesion and accessory molecules

Adhesion and accessory molecules play a critical role in T-cell activation and effector function in general and in tumor cell recognition and lysis in particular. We investigated the contribution of CD2, CD3, CD11a/CD18, CD54 and CD58 molecules in T lymphocyte-tumor cell interactions mediated by chimeric immunoglobulin receptors. The chimeric receptor is composed of a single chain antibody binding site and a gamma-chain signal transducing molecule (scFv/gamma). T lymphocytes expressing such scFv/gamma receptors recognize the G250 Ag on renal cell carcinoma (RCC) in an major histocompatibility complex (MHC)-unrestricted manner and exert RCC selective cytolysis. A coregulatory role for CD2, CD3 and CD11a/CD18 molecules in scFv/gamma-mediated cytolysis was demonstrated using monoclonal antibody (MAb)-induced inhibition of scFv/gamma-mediated cytolysis. The inhibition of lysis was not due to inhibition of cytotoxic T lymphocyte (CTL)-target cell conjugation but rather to a post-conjugate signaling event. Binding of CD54 and CD58 MAbs to the RCC did not inhibit cytolysis of RCC cells that expressed high levels of both CD54 and the G250 antigen (Ag) (A75), whereas cytolysis of RCC expressing intermediate levels of CD54 and G250 Ag (SK-RC-17 cl.4) was partly inhibited by the CD54 MAb. Binding of low concentrations of G250 MAb to RCC (A75) rendered these cells sensitive to CD54 MAb inhibition, demonstrating a direct functional relation between G250 Ag expression level and adhesion molecules. Taken together, our findings indicate a coregulatory role for CD2, CD3 and CD11a/CD18 molecules in the scFv/gamma-mediated cytolysis of tumor cells and show that the requirement of CD11a/CD18-CD54 interactions is dependent on the level of free Ag. This make these gene-transduced T lymphocytes attractive tools for adoptive immunogene therapy of cancer.

CD36 is rapidly and transiently upregulated on phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes. Analysis by a new monoclonal antibody (UN7)

The monoclonal antibody (mAb) UN7, clustered as an anti-CD36 mAb, has been used to test the cell surface expression of CD36 on peripheral blood lymphocytes (PBL) following mitogenic stimulation. CD36, scarcely expressed on resting cell membranes, was rapidly upregulated on PBL after phytohemagglutinin (PHA) stimulation. The antigen was detected on the cell surface after 15 min of stimulation, increased rapidly by 60 min and peaked between 3 and 12 h, declining thereafter. The inhibition of protein synthesis by cycloheximide did not modify the PHA-induced expression of CD36. Neither the anti-CD3 OKT3 mAb nor the anti-CD2 BIL 2.29 and 9.1 mAbs induced any significant upregulation of the molecule. The addition of anti-CD28 15E8 mAb or IL-2 or IFN-gamma to PHA or anti-CD3 or anti-CD2 mAbs did not influence the pattern of CD36 expression. The phorbol-2-myristate-13-acetate (PMA), alone or in combination with ionomycin, was unable to activate the expression of CD36, while it inhibited the PHA-induced upregulation. The PHA-induced upregulation of CD36 was partially inhibited by the addition of LY294002 or wortmannin, while not affected by that of calphostin C. Thus, CD36 was found to be early and transiently upregulated by PHA stimulation on PBL. The rapid modulation of the molecule was not related to new protein synthesis, but was probably due to the insertion into the plasma membrane of a presynthetized protein pool.

The TCR-Binding Region of the HLA Class I α2 Domain Signals Rapid Fas-Independent Cell Death: A Direct Pathway for T Cell-Mediated Killing of Target Cells?

TCR binding to an MHC class I/peptide complex is a central event in CTL-mediated elimination of target cells. In this study, we demonstrate that specific activation of the TCR-binding region of the HLA-A2 class I α2 domain induces apoptotic cell death. mAbs to this region rapidly induced apoptosis of HLA-A2-expressing Jurkat E11 cells, as determined by morphologic changes, phosphatidylserine exposure on the cell surface, and propidium iodide uptake. In contrast, apoptosis was not induced following culture with mAbs directed to other regions of the class I molecule. Death signaling by class I molecules is apparently dependent on coreceptor activation, as apoptosis is also signaled by HLA-A2 molecules, where the intracytoplasmic residues were deleted. HLA class I α2-mediated cell death appeared to proceed independent of the Fas pathway. Compared with apoptotic signaling by Fas ligation, HLA class I α2-mediated responses displayed a faster time course and could be observed within 30 min. Furthermore, class I α2-induced cell death did not involve observable DNA fragmentation. The apoptotic response was not affected significantly by peptide inhibitors of IL-1β converting enzyme (ICE)-like proteases and CPP32. Taken together, activation of the TCR-binding domain of the class I α2 helix may result in apoptotic signaling apparently dependent on a novel death pathway. Thus, target HLA class I molecules may directly signal apoptotic cell death following proper ligation by the TCR.

Monoallelic expression of the interleukin-2 locus

The lymphokine interleukin-2 (IL-2) is responsible for autocrine cell cycle progression and regulation of immune responses. Uncontrolled secretion of IL-2 results in adverse reactions ranging from anergy, to aberrant T cell activation, to autoimmunity. With the use of fluorescent in situ hybridization and single-cell polymerase chain reaction in cells with different IL-2 alleles, IL-2 expression in mature thymocytes and T cells was found to be tightly controlled by monoallelic expression. Because IL-2 is encoded at a nonimprinted autosomal locus, this result represents an unusual regulatory mode for controlling the precise expression of a single gene.

Dipeptidyl-peptidase IV/CD26 on T cells: analysis of an alternative T-cell activation pathway

CD26 is a proteolytic enzyme (dipeptidyl-peptidase IV) with a wide tissue distribution and a unique specificity that was already described 27 years ago. CD26 is expressed on a fraction of resting T cells at low density but is strongly upregulated following T-cell activation. Recent results indicate that CD26 is a multifunctional molecule that may have important functions on T cells and in the immune system. It is associated with molecules of immunological importance such as the protein tyrosine phosphatase CD45 and adenosine deaminase (ADA) on the cell surface. Synthetic inhibitors of the enzymatic activity of CD26 have been shown to suppress certain immune reactions in vitro and in vivo. An interesting feature of CD26 is its ability to transmit a transmembrane signal to trigger functional programs in T cells. This triggering requires crosslinking of CD26 on a cell membrane. The enzymatic activity of CD26 is not obligatory for the activation of T cells via CD26. Since CD26 is a type II membrane protein with only six intracellular amino acids, it must deliver its signal via a signal-transducing molecule. Signaling is dependent on the expression of the T-cell receptor (TCR) complex with a special need for a functional zeta-chain. In this context the zeta-chain of the TCR complex is required for CD26-mediated signaling but, in contrast to other co-stimulatory molecules such as the CD2 molecule, is not sufficient for triggering the T cell.

Enrichment of antigen-specific T lymphocytes by panning on immobilized MHC-peptide complexes

Numerous studies have focused on characterizing and monitoring antigen-specific T cells during the course of an immune response. Mostly indirect methods were used to circumvent the low frequency of T cell precursors and the inherent complexity of T cell receptor (TcR)-MHC-peptide interactions. Here, we took advantage of peptide-specific adhesion induced by immobilized MHC-peptide complexes. We describe a simple technique which allows enrichment in antigen-specific T lymphocytes among a heterogeneous CD8+ T cell population. Enrichment of T cells according to their specificity should facilitate their characterization and provide an attractive tool for immunotherapy.

T cell responses to human type II collagen in patients with rheumatoid arthritis and healthy controls

OBJECTIVE

To study the prevalence of T cell responses to human type II collagen (CII) in patients with rheumatoid arthritis (RA) with or without antibodies to CII, and in healthy controls.

METHODS

Assays were performed to study T cell proliferative responses to CII in peripheral blood from 69 patients with RA (11 with anti-CII antibodies and 58 without) and 28 healthy controls. Further analysis was made of the time course of the response and the epitopic specificity, using peptides derived from the cyanogen bromide 11 (CB11) fragment of CII.

RESULTS

Significant proliferative responses to CII were found in 50% of patients with anti-CII, 5.3% of RA patients without these antibodies, and 35.7% of healthy controls. Responses in RA patients differed from those in healthy controls; the former had kinetics suggestive of a recall response and the latter that of a primary response. Some common epitopes within CB11 were recognized by T cells from patients and controls.

CONCLUSION

Proliferative T cell responses to CII occur in some healthy individuals, suggesting that thymic tolerance for this antigen may be incomplete. Most patients with RA have no evidence of a T cell response to CII, possibly indicating the development of peripheral tolerance to this antigen as a consequence of cartilage breakdown. However, in a minority of patients, T and B cell responses to CII persist, and may contribute to joint damage.

Clustering the adhesion molecules VLA-4 (CD49d/CD29) in Jurkat T cells or VCAM-1 (CD106) in endothelial (ECV 304) cells activates the phosphoinositide pathway and triggers Ca2+ mobilization

Ligation of very late antigen (VLA)-4 (alpha 4 beta 1 integrin) with a cross-linked anti-alpha 4 subunit monoclonal antibody (mAb) triggered a biphasic Ca2+ response in Jurkat cell populations and in peripheral human lymphocytes. Cross-linking vascular cell adhesion molecule (VCAM)-1 (the counter-receptor of VLA-4) in ECV 304 endothelial cells generated a biphasic Ca2+ response. Tumor necrosis factor-alpha-primed human umbilical cord vascular endothelial cells also responded to the cross-linked mAb with a biphasic Ca2+ profile. Ligated VLA-4 (Jurkat cells) or VCAM-1 (ECV 304) stimulated the production of myo-inositol 1,4,5-trisphosphate. ECV 304 cells induced a biphasic Ca2+ response in Fura2-loaded Jurkat cells, whereas a transient response was observed when Jurkat cells were added to Fura2-loaded ECV 304 cells. The Ca2+ responses in these experiments involved VLA-4/VCAM-1 interactions since they were significantly reduced (approximately 80%) by prior treatment of the target cells with the relevant noncross-linked mAb. Close contact between the cells triggered mutual Ca2+ signaling as shown by spectrofluorimetric and confocal microscopy time-dependent recordings. Fibronectin and its CS-1 fragment (V25) triggered a sustained Ca2+ response in Jurkat cells (confocal microscopy). Our results suggest that the VLA-4 and VCAM-1 adhesion molecules can transduce a signal that involves activation of the phosphoinositide pathway and the mobilization of Ca2+.

Co-stimulation in T cell responses

Antigen-specific T cell responses have primarily been considered in terms of activation signals delivered through the TCR and the co-stimulatory molecule CD28. In the past few years, studies have demonstrated the critical importance of inhibitory signals for regulating lymphocyte activation. CD28 and its homologue cytotoxic T lymphocyte antigen-4 (CTLA-4) share the same counter-receptors on antigen-presenting cells, but recent experiments have shown that CD28 and CTLA-4 have opposite effects on T cell activation. The mechanisms responsible for integrating these activation and inhibitory signals at the cellular and molecular levels are just beginning to be elucidated.

Bacterial cell wall products increase monocyte HLA-DR and ICAM-1 without affecting lymphocyte CD18 expression

Bacterial cell wall products such as lipopolysaccharide (LPS) and muramyl dipeptide (MDP) have the capacity to enhance immune responses to antigens. The expression of surface class II major histocompatibility antigens and the costimulatory receptors CD18 and CD54/ICAM-1 (intercellular adhesion molecule) was used to evaluate the comparative influence of these immunostimulators. On monocytes, both LPS and MDP increased the expression of human leukocyte antigen (HLA)-DR (maximal at 6 hr), CD18 (maximal at 1-3 hr), and ICAM-1 (maximal at 18-24 hr for LPS and 12 hr for MDP) without increasing the production of superoxide. MDP-induced ICAM-1 expression on monocytes returned to baseline values after 12 hr. On lymphocytes, only LPS increased ICAM-1 (after 18 hr) without affecting CD18, and a differential analysis demonstrated a generalized ICAM-1 upregulation in lymphocyte subsets after 18 hr: the most pronounced effect was measured in natural killer cells, followed by CD8(+) T cells, B cells, and CD4(+) T cells. MDP did not alter ICAM-1 or CD18 expression on lymphocytes. These similar but smaller effects of MDP may, in part, explain the lesser toxicity of MDP when compared to LPS.

Regulation of cell signaling by the protein tyrosine phosphatases, CD45 and SHP-1

An equilibrium between positive and negative regulation of immunoreceptor signaling leads to the proper execution of lymphocyte activation. Tyrosine phosphorylation is the initial event in antigen receptor-induced lymphocyte activation. It is generally accepted that protein tyrosine kinases are involved in positive regulation, whereas protein tyrosine phosphatases are important for the negative regulation of tyrosine phosphorylation-dependent processes. However, the interaction between protein tyrosine kinases and protein tyrosine phosphatases is complex. This article discusses the role of two protein tyrosine phosphatases. CD45 and SHP-1, in the regulation of immunoreceptor signaling. SHP-1 acts as a negative regulator for several immunoreceptors, including those for T- and B-cell antigen receptors. The major role of CD45 is in the positive regulation of T- and B-cell antigen receptor signaling.

Structure and function of the CD94 C-type lectin receptor complex involved in recognition of HLA class I molecules

A multigene family of immunoglobulin superfamily (Ig-SF) killer cell inhibitory receptors (KIRs) specifically recognize HLA class I molecules, while the interaction with H-2 products is mediated by members of the murine Ly49 C-type lectin family. A common structural feature of these receptors with inhibitory function is the presence of cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIMs) that couple them to SHP phosphatases. Strong support for the involvement of the CD94 C-type lectin receptor complex in NK cell-mediated recognition of Bw6+ HLA-B, HLA-A and HLA-C alleles has been obtained. The cloned CD94 molecule covalently assembles with at least two different glycoproteins (43 kDa and 39 kDa) to form functional receptors. NK cells inhibited upon HLA recognition express the CD94/p43 dimer, whose specificity for HLA molecules partially overlaps the Ig-SF receptor system. By contrast, NK clones bearing the homologous CD94/p39 receptor are triggered upon its ligation by CD94-specific mAbs. Remarkably, a set of Ig-SF receptors (p50) homologous to p58 KIRs also display an activating function. CD94-associated molecules belong to the NKG2 family of C-type lectins; the NKG2-A gene encodes for the p43 subunit, which contains cytoplasmic ITIMS. Expression of the different CD94 heterodimeric receptors will enable precise analysis of their putative interaction with HLA class I molecules.

Premature ovarian failure and ovarian autoimmunity

Premature ovarian failure (POF) is defined as a syndrome characterized by menopause before the age of 40 yr. The patients suffer from anovulation and hypoestrogenism. Approximately 1% of women will experience menopause before the age of 40 yr. POF is a heterogeneous disorder with a multicausal pathogenesis involving chromosomal, genetic, enzymatic, infectious, and iatrogenic causes. There remains, however, a group of POF patients without a known etiology, the so-called "idiopathic" form. An autoimmune etiology is hypothesized for the POF cases with a concomitant Addison's disease and/or oöphoritis. It is concluded in this review that POF in association with adrenal autoimmunity and/or Addison's disease (2-10% of the idiopathic POF patients) is indeed an autoimmune disease. The following evidence warrants this view: 1) The presence of autoantibodies to steroid-producing cells in these patients; 2) The characterization of shared autoantigens between adrenal and ovarian steroid-producing cells; 3) The histological picture of the ovaries of such cases (lymphoplasmacellular infiltrate around steroid-producing cells); 4) The existence of various autoimmune animal models for this syndrome, which underlines the autoimmune nature of the disease. There is some circumstantial evidence for an autoimmune pathogenesis in idiopathic POF patients in the absence of adrenal autoimmunity or Addison's disease. Arguments in support of this are: 1) The presence of cellular immune abnormalities in this POF patient group reminiscent of endocrine autoimmune diseases such as IDDM, Graves' disease, and Addison's disease; 2) The more than normal association with IDDM and myasthenia gravis. Data on the presence of various ovarian autoantibodies and anti-receptor antibodies in these patients are, however, inconclusive and need further evaluation. A strong argument against an autoimmune pathogenesis of POF in these patients is the nearly absent histological confirmation (the presence of an oöphoritis) in these cases (< 3%). However, in animal models using ZP immunization, similar follicular depletion and fibrosis (as in the POF women) can be detected. Accepting the concept that POF is a heterogenous disorder in which some of the idiopathic forms are based on an abnormal self-recognition by the immune system will lead to new approaches in the treatment of infertility of these patients. There are already a few reports on a successful ovulation-inducing treatment of selected POF patients (those with other autoimmune phenomena) with immunomodulating therapies, such as high dosages of corticosteroids (288-292).

The CD94/NKG2 C-type lectin receptor complex: involvement in NK cell-mediated recognition of HLA class I molecules

A multigene family to human Ig-SF receptors and members of the murine Ly49 C-type lectin family are involved in natural killer (NK) cell-mediated recognition of MHC class I molecules. The human CD94 glycoprotein covalently assembles with different C-type lectins of the NKG2 family. By functional criteria, the CD94/NKG2-A (kp43) receptor complex appears also involved in NK cell-mediated recognition of different HLA class I allotypes. Similarly to the other NK inhibitory receptors, NKG2-A contains cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIMS). By contrast, NK clones bearing different receptor complex (CD94/p39) are triggered upon ligation by CD94-specific monoclonal antibodies (MAbs); the p39 subunit is likely encoded by other member(s) of the NKG2 family. Expression of different CD94/NKG2 complexes is warranted to precisely assess their specific interaction with HLA class I molecules, and the molecular basis for their divergent functional properties.

Correlation between CD29 density on CD8+ lymphocytes and serum IgG in systemic lupus erythematosus

The purpose of this paper is to establish whether there is increased lymphocyte adhesion molecule density in systemic lupus erythematosus (SLE), which could alter the migration pathways and activation thresholds of lymphocytes and thus contribute to the pathogenesis of the disease. We analysed the CD11a, CD29 and CD2 bound antibody molecule (bam) density on the CD4+ and CD8+ CAMhigh (primed) lymphocytes of 28 SLE patients (8 active and 20 inactive by BILAG), using reproducible flow cytometric measurements, standardized with fluorescent beads and antibodies of known fluorescein: protein ratios. In a second patient cohort (17 patients), we investigated whether CD29 density on CD8+ cells correlated with measures of humoral (serum IgG) or cellular (urine neopterin) activation. In the first cohort, 36% of patients had elevated CD29 (beta 1 integrin) density on CD8+ cells. In the second cohort, CD29 density on CD8+ cells was found to be closely associated with total plasma IgG (r = 0.71, P = 0.001), but not with urine neopterin, disease activity (BILAG) or drug treatment. We conclude that CD29 on CD8+ cells is associated with B cell activation in SLE.

Activation features of intraepithelial gamma delta T-cells of the murine vagina

The epithelium of the murine vagina contains a resident population of gamma delta T-cells that expresses a homogenous Vgamma4/Vdelta1 TCR lacking N-region junctional diversity, implying that these T-cells recognize a very limited array of antigenic structures. The vaginal gamma delta T-cells express a pattern of surface markers characteristic of memory/effector T-cells that have previously been activated. Although vaginal gamma delta T-cells do not express the major costimulatory molecules CD28 and CD2, they do proliferate in response to a systemically delivered anti gamma delta TCR stimulus. Vaginal gamma delta T-cells contain mRNA that encodes the keratinocyte growth factor raising the possibility that these cells play a role in the repair of vaginal epithelium following injury. While the antigen recognized by the vaginal gamma delta TCR is unknown, a model is proposed which attempts to relate some of the unusual phenotypic features of vaginal gamma delta T-cells to the physiological injury and shedding of vaginal epithelium that occurs during the estrous cycle.