Epitope mapping of neutralizing TSST-1 specific antibodies induced by immunization with toxin or toxoids

Toxic shock syndrome toxin-1 (TSST-1), a superantigen produced by Staphylococcus aureus, is a potent stimulator of the immune system. T-cells are activated by crosslinking of MHC class II molecules on antigen presenting cells with T-cell receptors (TCR). TSST-1 is associated with the majority of the cases of menstrual staphylococcal toxic shock, a severe and life-threatening multisystem disorder. Even though antibody mediated protection has been studied, information on antibody specificity directed to individual antigenic determinants of the protein is incomplete. To obtain immunogens with low toxicity, we generated a double-site mutant (dmTSST-1), modified at solvent-exposed residues predicted to be important for both MHC class II and TCR binding, and detoxified recombinantly expressed TSST-1 (rTSST-1) as well as native TSST-1 (nTSST-1) isolated from Staphylococcus aureus by treatment with formaldehyde. Rabbits were immunized with rTSST-1, nTSST-1, dmTSST-1, and formaldehyde inactivated toxoids. The sera obtained were used to map the antigen-reactive regions of the molecule and to identify specificities of antibodies induced by immunization with the different antigens. To detect linear antigenic epitopes of TSST-1 the reactivity of the sera with 11-meric peptides having an overhang of four residues, covering the entire molecule of TSST-1, have been studied. We found that sera of TSST-1 immunized rabbits predominantly reacted with N-terminal residues 1-15, while sera generated with formaldehyde inactivated toxoid recognized a total of 7 regions located at the N- and C-terminus and internal sites of TSST-1. Despite different specificities all sera were able to inhibit TSST-1 induced proliferation of human mononuclear cells.

Mutation in a winged-helix DNA-binding motif causes atypical bare lymphocyte syndrome

Bare lymphocyte syndrome (BLS) is an autosomal recessive severe-combined immunodeficiency that can result from mutations in four different transcription factors that regulate the expression of major histocompatibility complex (MHC) class II genes. We have identified here the defective gene that is responsible for the phenotype of the putative fifth BLS complementation group. The mutation was found in the regulatory factor that binds X-box 5 (RFX5) and was mapped to one of the arginines in a DNA-binding surface of this protein. Its wild-type counterpart restored binding of the RFX complex to DNA, transcription of all MHC class II genes and the appearance of these determinants on the surface of BLS cells.

Impaired primary immune response in type-1 diabetes: results from a controlled vaccination study

Patients with diabetes have an increased risk for infections, but information on their adoptive immunity is incomplete and contradictory. Twenty patients with diabetes type-1 and 20 patients with type-2 diabetes were vaccinated with T-cell-dependent primary protein antigens (hepatitis A viral antigen, HAV; diphtheria toxoid) and a T-cell-independent polysaccharide antigen (pneumococcal polysaccharide). In parallel, the proliferative response of CD4+ T-cells to the primary protein antigens keyhole limpet hemocyanin (KLH) and sperm whale myoglobin (SWM) was measured in vitro using monocyte-derived dendritic cells (MDDC) as antigen-presenting cells. Compared to healthy controls, type-1 diabetes patients mounted a significantly impaired primary antibody response to hepatitis A vaccine (median HAV antibody titer after the first vaccination, 53 IU/L in diabetic patients vs 212 IU/L in the controls, P = 0.017) and diphtheria toxoid (median serum antibodies after vaccination, patients, 0.94 IU/ml, controls, 6.38 IU/ml, P = 0.004), while the response to pneumococcal polysaccharide was normal. Type-2 diabetes patients had a comparable metabolic dysregulation but showed a normal antibody response following vaccination, demonstrating that the effect was not due to hyperglycemia. Antigen-induced interferon-gamma and interleukin-13 release was reduced in type-1 diabetes patients, localizing the impairment to the level of antigen-presenting cell-T-cell interaction. In addition, the proliferative response of CD4+ T-cells derived from type-1 diabetes patients to KLH and SWM was significantly reduced (P < or = 0.01). FACS analysis of CD80 (B7.1), CD86 (B7.2), and HLA-DR expression on MDDC could not demonstrate significant differences in the expression of these molecules between type-1 and type-2 diabetes patients and healthy controls. An association of low HAV antibody response with HLA-DR3,4 expression in the patients was shown. Our results indicate that the primary antibody response to T-cell dependent antigens as well as the T-cell response to primary protein antigens is reduced in type-1 diabetes patients and that additional booster immunization can overcome the defect.

Double mutant and formaldehyde inactivated TSST-1 as vaccine candidates for TSST-1-induced toxic shock syndrome

Up to now there is no treatment for staphylococcal toxic shock syndrome, a disease mainly induced by toxic shock syndrome toxin-1(TSST-1). There is great demand in finding means to control the disease, one of them is the development of an effective and safe vaccine against TSST-1. In this study we constructed a series of vaccine candidates and investigated their biological activity, toxicity, and potential to invoke an immune response. TSST-1 was isolated from Stahylococcus aureus supernatants and recombinantly expressed as a N-terminal 6x histidine-tagged protein in Escherichia coli. In order to obtain molecules with minimal toxicity we constructed single mutants (G31R and H135A) and one double mutant (G31R/H135A) with both residues exchanged. We also detoxified native TSST-1 isolated from S. aureus, and recombinantly expressed TSST-1 by treatment with formaldehyde. Functional activity of native and recombinant TSST-1 and grade of inocuity of mutants and toxoids was determined by investigating mitogenity, T-cell activation, and cytokine release upon stimulation of human mononuclear cells with the vaccine candidates. All substances were tested in a rabbit immunization study. After primary immunization and three additional boosts all vaccinated animals developed antibody titers against TSST-1 and were protected against challenge with a lethal doses of superantigen potentiated with lipopolysaccharide.

Residual expression of functional MHC class II molecules in twin brothers with MHC class II deficiency is cell type specific

We examined major histocompatibility complex (MHC) class II expression in B cells, peripheral blood monocytes, activated T cells, epidermal Langerhans cells, monocyte-derived dendritic cells, dermal microvascular endothelial cells (DMEC) and fibroblasts of twin brothers with MHC class II deficiency. Although residual human leucocyte antigen (HLA)-DR expression was found on a subpopulation of epidermal Langerhans cells and a subset of peripheral blood monocyte-derived dendritic cells, the patients' B cells, monocytes and activated T cells were HLA-DR negative. After treatment with interferon-gamma (IFN-gamma), the patients' DMEC expressed HLA-DR but not -DP and -DQ at the protein and mRNA level, whereas IFN-gamma failed to induce HLA-DR expression on dermal fibroblasts. The patients' monocyte-derived dendritic cells were capable of processing and presenting tetanus toxoid to autologous T cells, and patient-derived DMEC induced the proliferation of allogeneic CD4(+) T cells in an MHC class II-restricted fashion, indicating that the observed residual MHC class II surface expression was functional. The findings reported show that the defect encountered in these patients is not necessarily expressed to the same extent in different cell lineages, which is relevant for the understanding of the patients' phenotype and also illustrates that only small amounts of MHC class II are needed to mount a functional cellular immune response in vivo.

Immune response to the herpes simplex type 1 regulatory proteins ICP8 and VP16 in infected persons

The specific immune responses directed against the viral single stranded (ss) DNA binding protein ICP8 and the transactivator of immediate early (IE) gene expression VP16 (alpha-trans inducing factor, Vmw65) in HSV type 1 seropositive humans were examined. The results described in this paper indicate that neither ICP8 nor VP16 were able to induce a recall response in lymphocytes of healthy HSV seropositive individuals without recurrent infection, although CD4+ T cells purified from these individuals responded to both viral proteins in vitro when monocyte derived dendritic cells were used as antigen presenting cells. A recall response, however, could be induced to both viral proteins in T cells of patients with recurrent HSV infections when blood monocytes were used. Moreover, ICP8- and VP16-specific antibodies could be detected in the serum of patients with recurrent HSV infections whereas, in contrast, these antibodies were virtually absent in healthy HSV seropositive individuals without recurrences. These data represent the first systematic study of the immunological properties of ICP8 in humans, indicating a significant difference in the response to the essential viral regulators ICP8 and VP16 in HSV-1 seropositive healthy individuals as opposed to patients with recurrent HSV-1 infections.

Transient increase in mitogen-induced lymphoproliferative responses in patients with testicular cancer after BEP chemotherapy

OBJECTIVES

To investigate the impact of polychemotherapy on cellular immunity in patients with testicular cancer.

METHODS

Lymphocyte subpopulations, lymphoproliferative responses to mitogenic stimulation, and mitogen-induced release of soluble interleukin-2 receptor from peripheral blood mononuclear cells were investigated in 15 patients with testicular germ cell tumors a median of 61 months (range 7 to 73) after polychemotherapy with bleomycin, etoposide, and cisplatin (BEP).

RESULTS

The numbers of peripheral blood T cells (CD3+), CD4+ and CD8+ subsets, and lymphoproliferative responses to pokeweed mitogen, phytohemagglutinin, and concanavalin A in patients were comparable to those of healthy control subjects. When two groups of patients were formed according to elapsed time from BEP polychemotherapy and study onset (group A, 12 months and group B, 69 months after termination of BEP), a significant increase in lymphoproliferative response to concanavalin A (P <0.05) was found in group A 1 year after chemotherapy.

CONCLUSIONS

BEP chemotherapy administered to patients with testicular cancer does not result in impairment of cellular immunity but rather leads to a significant increase in the capacity of patients' lymphocytes to respond to mitogenic stimulation up to 1 year after polychemotherapy. Moreover, the increased T-cell activity found after BEP therapy may contribute to the high rate of long-term complete remission.

Long-term decrease of CD4+CD45RA+ T cells and impaired primary immune response after post-traumatic splenectomy

Congenital or acquired absence of the spleen and functional hyposplenism are associated with abnormalities of host defence such as an increased susceptibility to infection with encapsulated bacteria. The effects of the lack of the spleen on cell-mediated immunity are largely unknown. In the present study we have investigated peripheral blood lymphocyte subpopulations in healthy adults who had undergone splenectomy because of severe abdominal trauma > 4 years before the study. The results show a significant reduction in the percentage of CD4+ T cells due to a selective and long-term decrease in the percentage of CD4+CD45RA+ lymphocytes, the CD4+ T-cell subset mainly involved in primary immune responses to newly encountered antigens. Levels of the reciprocal CD45RO+CD4+ T-cell subset were comparable between splenectomized and control individuals, as were lymphoproliferative responses and IFN-gamma production to recall antigens. Decreased levels of CD4+CD45RA+ cells were accompanied by an impairment in primary immune responsiveness, as assessed by investigating T-cell proliferation to stimulation with keyhole limpet haemocyanin and by measuring antibody responses following primary immunization with a clinically relevant T-dependent antigen, hepatitis A vaccine, in vivo. These findings suggest a possible role of the spleen in the generation, maintenance and/or differentiation of naive, unprimed T cells or their precursors, which might have a possible functional relevance for primary immune responses following splenectomy.

Effect of intravenous immunoglobulin on steroid consumption in patients with severe asthma: a double-blind, placebo-controlled, randomized trial

BACKGROUND

There is a significant group of patients with severe asthma who require chronic use of systemic steroids for control of their disease. These patients are at risk for severe side effects from oral steroids. Intravenous immunoglobulin (IVIG) has immunomodulatory properties, and a few open-label trials have suggested its possible benefit in individuals with severe asthma.

OBJECTIVE

This study was designed to assess the potential benefit of IVIG as a steroid-sparing agent in patients with severe asthma.

METHODS

Thirty-eight immunocompetent steroid-requiring patients with severe asthma were randomly enrolled in a double-blind, placebo-controlled trial of IVIG.

RESULTS

Of the 38 patients enrolled, 28 patients completed the study. A significant reduction in oral steroid requirement was observed in both the IVIG-treated (n = 16) and the placebo-treated (n = 12) patients. Further exploration of the results showed that IVIG, but not placebo, had a significant steroid-sparing effect in patients requiring high doses of oral steroids (ie, >2000 mg in the year before the study). Within this subgroup, IVIG treatment (n = 9) resulted in a significant decrease in oral steroid requirement, with a median of 16.4 mg/day during the pretreatment period to 3 mg/day during the treatment phase (P =. 0078). No significant decrease in oral steroid requirement was observed in placebo-treated patients (n = 8) within this subgroup. Objective and subjective parameters of the patients' asthma were unchanged in spite of the steroid tapering achieved in the group treated with IVIG.

CONCLUSION

IVIG may be a useful steroid-sparing agent in patients with severe asthma requiring high doses of oral steroids.

Nitrocellulose particles adsorbed to immunoglobulins are a new and effective approach to induce cell activation dependent on receptor aggregation

Nitrocellulose (NC) has proved to be a versatile tool for the isolation and characterization of various biomolecules. In this report we extend its scope by using antibody-coated NC particles to cross-link molecules on the surface of living cells. Ligation of receptors in Jurkat cells with NC-bound specific antibodies induced protein tyrosine phosphorylation patterns of cellular proteins comparable to conventional antibody cross-linking. In addition, the present study shows that application of NC particles coated with human IgA significantly activated monocytic cells via the Fc alpha receptor (Fc alphaR), whereas cross-linking of receptor-ligand complexes with isotype-specific antibody was less efficient. Subsequent immunoprecipitation and immunoblot analysis of aggregated Fc receptors (FcRs) complexed to Ig-adsorbed particles permits fast identification of molecules involved in the transmission of signals. Therefore, ligand-coated NC particles can be used to examine receptor-mediated cell activation events dependent upon extensive receptor aggregation.

Physical and functional association of Fc alpha R with protein tyrosine kinase Lyn

In this report, we show that the Src family nonreceptor protein tyrosine kinase (PTK) Lyn associates with aggregated IgA Fc receptor (Fc alpha R) in the monocytic cell line THP-1. Receptor aggregation and subsequent immunoprecipitation of receptor complexes with huIgA adsorbed to nitrocellulose particles shows that Lyn associates with Fc alpha R by a mechanism sensitive to short treatment with the Src family-selective inhibitor PP1. However, interaction of Lyn with IgG Fc receptor (Fc gamma R) in THP-1 cells was unaffected by short treatment with the PTK inhibitor. Cross-linking of Fc alpha R induced tyrosine phosphorylation of several cellular proteins, including p72Syk, which appears to be a major target of early PTK activity. Unexpectedly, in vitro kinase assays showed that Fc alpha R aggregation-induced tyrosine phosphorylation of Syk did not result in upregulation of Syk activity. Despite the lack of enhanced Syk kinase activity, downstream signaling after Fc alpha R cross-linking was functional and induced the release of significant amounts of interleukin-1 receptor antagonist and interleukin-8. The induction of cytokine release was completely blocked by PP1, thus confirming the biological significance of the association of Lyn with aggregated Fc alpha R. Our data show that early signal transduction after Fc alpha R cross-linking as well as Fc alpha R-mediated activation of cellular effector functions depends on Src family kinase activity. The Src-family PTK involved in Fc alpha R-mediated tyrosine phosphorylation appears to be Lyn, which coprecipitated with aggregated Fc alpha R complexes.

Defective integration of activating signals derived from the T cell receptor (TCR) and costimulatory molecules in both CD4+ and CD8+ T lymphocytes of common variable immunodeficiency (CVID) patients

CVID is characterized by hypogammaglobulinaemia and impaired antibody production. Previous studies demonstrated defects at the T cell level. In the present study the response of purified CD4+ and CD8+ T lymphocytes to stimulation with anti-TCR monoclonal antibody (the first signal) in combination with anti-CD4 or anti-CD8, anti-CD2 and anti-CD28 MoAbs (the costimulatory signals) was investigated. Both CD4+ and CD8+ T cells from the patients showed significantly reduced IL-2 release following stimulation via TCR and costimulation via CD4 or CD8 and CD2, respectively. However, normal IL-2 production following TCR plus phorbol myristate acetate (PMA) costimulation and normal expression of an early activation marker, CD69, after TCR+CD28 stimulation indicated that TCR was able to transduce a signal. Furthermore, both IL-2 and IL-4 release were impaired in CD4+ lymphocytes following TCR+CD28 stimulation. In addition, stimulation via TCR+CD28 resulted in significantly decreased expression of CD40 ligand in the patients. These results suggest that the integration of activating signals derived from the TCR and costimulatory molecules is defective in CVID patients; the defect is not confined to costimulation via a single molecule, or restricted to cells producing Th1-type cytokines such as IL-2, and is expressed in both CD4+ and CD8+ T cell subsets.

Inhibition of IL-10 protein synthesis induces major histocompatibility complex class II gene expression in class II-deficient patients

Major histocompatibility complex (MHC) class II deficiency is an inherited autosomal recessive combined immunodeficiency, characterized by a lack of constitutive expression of the human leukocyte antigen (HLA) class II genes. The patients investigated in this study are histoidentical twin brothers with a new phenotype in MHC class II deficiency. Examination of HLA-D locus genes in their fractionated peripheral mononuclear cells (MNCs) revealed an unusual and uncoordinated mRNA pattern. Here we analyzed the distribution of pro- and anti-inflammatory cytokines expressed in these patients' adherent and nonadherent MNCs. We show that gene expression of IL-1 alpha, IL-1 beta, IL-6, granulocyte-colony-stimulating factor, and IL-10 was induced in both cell fractions, whereas increased mRNA levels of interferon-gamma and the inducible nitric oxide synthase were exclusively detected in the patients' nonadherent MNCs. As IL-10 is known to be able to downregulate transcription of MHC class II and expression of IL-10 in the patients' MNCs was increased, we investigated the regulatory function of this cytokine. Interestingly, inhibition of IL-10 protein synthesis with IL-10-specific antisense oligonucleotide DNA (IL-10-AS-ODN) induced HLA-D locus genes in these MHC class II-deficient patients. Exposure of the nonadherent cell fraction to IL-10-AS-ODN resulted in a profound induction of a previously absent DR beta 1 and DP alpha gene expression. HLA-DQ beta mRNA levels, however, were increased in both the adherent and the nonadherent MNC population. Albeit expression of HLA-D locus genes was inducible via inhibition of IL-10 translation, surface expression of HLA class II antigens on the patients' MNCs was essentially negative. The data presented support the concept of a coordinated network of pro- and anti-inflammatory cytokine regulation and this network obviously has a significant role in the cell-type-specific regulation of MHC class II expression.

Antigen presentation by common variable immunodeficiency (CVID) B cells and monocytes is unimpaired

CVID is a primary immunodeficiency syndrome comprising a heterogeneous group of patients with hypogammaglobulinaemia and defective formation of specific antibodies. Previous studies demonstrated defective T cell responsiveness to antigen in a major subgroup of patients. In the present study we investigated the capacity of peripheral blood monocytes and Epstein-Barr virus (EBV)-transformed B cell lines from seven patients with CVID, including two patients expressing an extended MHC haplotype described to be associated with CVID, to present antigen (Tet. Tox.) to CD4+ antigen-specific T cell lines from healthy controls. The results presented show an unimpaired capacity of peripheral blood monocytes to present antigen in all patients studied. In addition, the present study demonstrates for the first time that CVID B cells function normally as antigen-presenting cells (APC). These findings indicate that expression of a certain MHC phenotype in CVID is not associated with a defect in the presentation of recall antigen by monocytes and B cells. Based on these studies, uptake, processing and re-expression of recall antigen in association with MHC class II molecules on the APC surface are functional and there is no indication for structural abnormalities of the MHC class II molecules expressed by the patients studied that could be essential for their function in antigen binding and presentation.

Anti-inflammatory properties of human serum IgA: induction of IL-1 receptor antagonist and Fc alpha R (CD89)-mediated down-regulation of tumour necrosis factor-alpha (TNF-alpha) and IL-6 in human monocytes

A deregulated expression and/or release of large amounts of inflammatory cytokines such as IL-1 and TNF-alpha accounts for most pathophysiological events in a variety of systemic inflammatory diseases, the effect being mediated by the interaction of these cytokines with their respective receptors. IL-1 receptor antagonist (IL-1Ra), mainly produced by monocytes/macrophages, is an inhibitor of IL-1 activity. The present study shows that human serum IgA induces significant IL-1Ra release in human peripheral blood mononuclear cells and adherent monocytes. IgA induced higher levels of IL-1Ra than Haemophilus influenzae type b (Hib) expressing lipopolysaccharide (LPS), purified LPS or phorbol myristate acetate (PMA), without induction of IL-1 beta release, and even inhibited LPS-induced IL-1 beta release. Induction of IL-1Ra by IgA could be detected both at the mRNA and protein levels in resting and activated monocytes. Ligation of Fc alpha R with MoAb My-43 or treatment with human serum IgA induced protein tyrosine phosphorylation in human monocytes, and herbimycin A, a specific inhibitor of protein tyrosine kinase activity, inhibited IgA-induced IL-1Ra production, suggesting that Fc alpha R-mediated induction of tyrosine phosphorylation is required for the IgA-induced stimulation of IL-1Ra release. In addition, triggering of Fc alpha R with MoAb specifically down-regulated TNF-alpha and IL-6 release in human monocytes activated with Hib. By the induction of IL-1Ra and down-regulation of the release of inflammatory cytokines such as IL-1 beta, TNF-alpha and IL-6, interaction of IgA with human monocytes may actively contribute to the regulation of the inflammatory response.

Immunomodulatory effect of immunoglobulins

IVIG is clearly indicated as the treatment of choice on the basis of large clinical trials in a number of inflammatory and autoimmune diseases, e.g. Kawasaki disease, ITP, Guillain-Barré syndrome, etc. According to in vitro studies various mechanisms have been identified whereby IgG could modify immunologically mediated and inflammatory diseases. Fc-receptor blockade as well as true down-modulation of Fc-receptors, acting as a sump for activated complement components, have been demonstrated at the cellular level and in experimental animals. The possibility of interfering with the idiotype network has been discussed in connection with autoimmune diseases. Down-regulation of inflammatory cytokines as well as an increase in the production and release of IL-1 receptor antagonist appears to be of importance in inflammatory processes. Clinical studies have proven the efficacy of IVIG. Basic research has demonstrated its possible mechanisms of action; however, the question of exactly which mechanisms are responsible for the clinical efficacy in certain diseases still awaits clarification.

Method for the isolation of biologically active monomeric immunoglobulin A from a plasma fraction

A purification method for immunoglobulin A (IgA) yielding monomeric IgA with a purity of over 97% has been developed. This procedure uses ethanol-precipitated plasma (Cohn fraction III precipitate) as the starting material and includes heparin-Sepharose adsorption, dextran sulfate and ammonium sulfate precipitation, hydroxyapatite chromatography, batch adsorption by an anion-exchange matrix and gel permeation. Additional protein G Sepharose treatment leads to an IgA preparation of greater than 99% purity. The isolated IgA presented with an IgA subclass distribution, equivalent to IgA in unfractionated plasma, and was biologically active, as was shown by its ability to down-modulate Haemophilus influenzae-b-induced IL-6 secretion of human monocytes.

Activation via the antigen receptor is impaired in T cells, but not in B cells from patients with common variable immunodeficiency

The patients included in this study belong to a subset of common variable immunodeficiency (CVID) patients whose peripheral blood T cells have a T cell receptor (TCR)-mediated activation defect leading to impaired expression of the interleukin (IL)-2 gene upon stimulation with recall antigens (tetanus toxoid, Escherichia coli) or superantigens (staphylococcal enterotoxins). In the present report we demonstrate that the patients' peripheral blood T cells failed to generate the second messenger inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) following stimulation with superantigen or mAb specific for the monomorphic region of the TCR beta-chain. Patients' T cell lines were also impaired in generating Ins(1,4,5)P3 when stimulated with tetanus toxoid-pulsed autologous monocytes. Addition of a second or third co-stimulatory signal provided by recombinant IL-2, CD28 or both had no effect on the Ins(1,4,5)P3 formation of the patients' antigen-driven T cell lines. The T cell activation defect, however, was not absolute, as Ins(1,4,5)P3 formation in the patients' T cells after phytohemagglutinin or aluminium fluoride stimulation was normal. The impairment in signal transduction via the T cell antigen receptor was limited to the patients' T cells, as no activation defect after ligation of surface immunoglobulin, the antigen receptor on B cells, could be detected.

Common variable immunodeficiency: clinical aspects and recent progress in identifying the immunological defect(s)

Common variable immunodeficiency (CVID) comprises a heterogeneous group of patients with as yet undefined genetic defects. Patients with CVID have in common a decrease in the levels of one or more serum immunoglobulin isotypes and a severe defect in the production of specific antibodies. Typically, the patients suffer from recurrent infections of the upper and lower respiratory tract or the gastrointestinal tract. In consequence of these infections patients may develop severe organ damage, such as chronic pulmonary disease with bronchiectases, leading to pulmonary failure. Early diagnosis of CVID is important, as antibody deficiency can efficiently be treated by regular intravenous IgG (IVIG) substitution therapy. IVIG therapy prevents the occurrence of further acute infectious episodes and the development of long-term complications. The basic immunological defect(s) in patients with CVID are still unknown. There is currently no convincing evidence for an intrinsic B-cell defect in patients with CVID. A defect in T-cell activation due to impaired signal transduction upon T-cell receptor triggering has been described in a large subgroup of patients with CVID. Defective T-cell activation may lead to an impairment in cognate T-B-cell interaction due to impaired expression of CD40 ligand and/or abnormalities in the production T-cell-derived cytokines required for fully functional B-cell activation, proliferation and/or differentiation which could indeed explain the impairment in antibody production present in CVID patients.

Molecular characterization of major histocompatibility complex class II gene expression and demonstration of antigen-specific T cell response indicate a new phenotype in class II-deficient patients

Major histocompatibility complex (MHC) class II deficiency is an inherited autosomal recessive combined immunodeficiency. The disease is known as bare lymphocyte syndrome (BLS). BLS is characterized by a lack of constitutive MHC class II expression on macrophages and B cells as well as a lack of induced MHC class II expression on cells other than professional antigen-presenting cells (APCs) due to the absence of mRNA and protein of the human leukocyte antigen (HLA) class II molecules, designated HLA-DR, -DQ, and -DP. The defect in gene expression is located at the transcriptional level and affects all class II genes simultaneously. Here we have analyzed transcription and protein expression of class II antigens in Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines and mononuclear cells (MNCs) of twin brothers. Whereas flow cytometric analysis failed to detect class II antigens on the cell surface of the patients' EBV-B cells and MNCs, examination of the genes coding for HLA-DR, -DQ, -DP, and the invariant chain (Ii) by reverse transcriptase-polymerase chain reaction amplification resulted in an unusual mRNA pattern in the B cell lines of the patients (HLA-DR alpha +, -DR beta, -DQ alpha +, -DQ beta -, -DP alpha -; -DP beta +, Ii+). In accordance with these findings no HLA-DR beta-specific protein was detected by immunoblotting, whereas low levels of HLA-DR alpha and normal levels of Ii were present. In contrast to EBV-B cells, the MNCs of both patients displayed a residual HLA-DR beta, -DQ beta, and -DP alpha mRNA signal. Furthermore, HLA-DR beta-specific protein was found in addition to HLA-DR alpha by immunoblotting of cell lysates, even though it was clearly decreased as compared with controls. Our results indicate that the defect in class II antigen expression is not necessarily present to the same extent in B cells and cells of other lineages. mRNA levels of HLA-DR beta were found to be enriched in adherent cells within the MNC fraction. Further investigations indicated that the MHC class II expressed is functional in antigen presentation, as the two boys' CD4+ T cells became activated and expressed interleukin-2R after stimulation of peripheral blood mononuclear cell cultures with recall antigen (tetanus toxoid). Furthermore, T cells tested in one of the two patients responded to both MHC class I and II allostimulation, and this response was inhibited by monoclonal antibodies of the respective specificity.(ABSTRACT TRUNCATED AT 400 WORDS)

Defective TCR surface expression associated with impaired TCR beta-chain assembly in a patient with cutaneous T-cell lymphoma

We report on a patient with cutaneous T-cell lymphoma (CTCL) of long-standing duration. Phenotypic analysis of his peripheral blood mononuclear cells revealed an increased CD4+ T-helper subset and a decreased CD8+ cytotoxic T-cell population. Eighty-three to ninety-three percent of the patient's CD4+ T cells in the peripheral blood and 70% of the CD4+ T cells in the lesional skin lacked surface expression of the TCR/CD3 complex and showed a clonal rearrangement pattern of the TCR gamma-chain gene (V11-J1/J2). The lack in TCR surface expression correlated with defective assembly of the TCR beta-chain. Although mRNA for the TCR constant region beta 1 was found in the patient's purified CD4+ TCR-CD3- T cells, no intracytoplasmic TCR beta protein was detectable. In contrast, the patient's purified CD4+ TCR-CD3- T cells not only expressed mRNA specific for the TCR alpha-chain and for all CD3 chains, but intracytoplasmic TCR alpha and CD3 epsilon proteins could also be found. The lack of TCR beta protein clearly explains the defective surface expression of the TCR/CD3 complex in the patient's malignant T cells.

Immunization of chimpanzees with recombinant gp160, but not infection with human immunodeficiency virus type 1, induces envelope-specific Th1 memory cells

The human immunodeficiency virus (HIV) type 1 envelope protein (recombinant [r] gp160)-induced T cell lymphokine release pattern of chimpanzees immunized with HIVIIIB rpg160 tested and compared with rpg160-induced lymphokine releases of T cells from unimmunized, HIV-1-infected chimpanzees. The results showed that infection of chimpanzees with HIV-1 did not induce rgp160-specific memory T cells (as evidenced by the lack of Th1 and 2 type lymphokine releases after rgp160 stimulation). In contrast, T cells of rgp160-immunized chimpanzees released Th1 type lymphokines upon stimulation with rgp160 of HIVIIIB, HIVMN, and HIVRF. release was comparable whether chimpanzees were immunized with rgp160 only or also challenged with HIV-1 and protected or not protected. Thus, rgp160 immunization leads to generation of Th1 type memory cells. Whether Th1 type responses contribute to protection against HIV-1 infection has yet to be clarified.