Regulating Vav1 phosphorylation by the SHP-1 tyrosine phosphatase is a fine-tuning mechanism for the negative regulation of DISC formation and Fas-mediated cell death signaling.

The actin cytoskeleton association is required for caspase 8-independent Fas/CD95 receptor internalization, a critical step for an optimal death-inducing signaling complex formation along the endocytic pathway, leading to efficient activation of the caspase cascade and, ultimately, cell death. However, the way in which this initiation phase of Fas receptor signaling is regulated is still unknown. We report herein that, in B cells, upon Fas engagement, the tyrosine phosphatase SHP-1-regulated Vav dephosphorylation, by downmodulating the Fas-ezrin-actin linkage is a fine-tune switch-off mechanism that the cell uses as a way to terminate the receptor internalization, controlling therefore the time and extent of the DISC formation and cell death.

Adjuvant effect of gamma-inulin is mediated by C3 fragments deposited on antigen-presenting cells.

The adjuvant effect of gamma-inulin, a strong activator of the alternative complement pathway, is well-known, but its exact mechanism is not revealed yet. Here, we show that macrophages, isolated from the peritoneal cavity of gamma-inulin-injected mice and used as antigen-presenting cells, enhance the proliferation of antigen-specific T-cells up to 2.5-fold when compared with macrophages of non-treated animals. This effect is abrogated by the presence of anti-C3 F(ab')2 fragments and by prior decomplementation of the donor animals with CVF. It is demonstrated that treatment of mice with the adjuvant results in deposition of C3-fragments onto the surface of peritoneal macrophages, as does in vitro incubation of the cells with gamma-inulin in the presence of fresh autologous serum. Prior incubation of macrophages with gamma-inulin plus serum in vitro enhances subsequent C3 production. Because it has been shown earlier that CR1/2 expressed on activated T-cells and interacting with covalently bound C3-fragments plays an important role in the augmentation of the adaptive response, our present results reveal a mechanism that contributes to the adjuvant effect of gamma-inulin and point to a further link between innate and adaptive immunity.

Two parallel routes of the complement-mediated antibody-dependent enhancement of HIV-1 infection.

OBJECTIVE: To study the mechanism of the complement-mediated antibody-dependent enhancement (C'-ADE) of HIV infection which may play a significant role in the progression of HIV-disease. METHODS: In vitro complement activating and complement-mediated HIV-infection enhancing abilities of three human anti-gp41 monoclonal antibodies (MAb) were tested. C'-ADE was estimated using HIV-1IIIB and CR2 (CD21)-carrying MT-4 target cells. Normal human serum (NHS), purified C1q, C1q-deficient (C1qD) and C2-deficient (C2D) human sera were applied as complement sources. RESULTS: All MAb mediated increased C1q binding to solid-phase gp41. All MAb had a marked dose-dependent and strictly complement-mediated HIV-infection enhancing effect. Mixtures of the MAb with purified C1q also significantly increased HIV-1 infection. C1qD serum had a markedly lower enhancing effect than NHS, which could be raised to normal level by addition of purified C1q. Pretreatment of the target cells with anti-CR2 antibodies only partially inhibited the enhancing effect of the MAb plus normal human serum. CONCLUSION: These novel findings indicate that besides the well-known facilitation of entry of HIV-1 by the interaction between virus-bound C3 fragments and CR2 present on the target cells, fixation of C1q to intact virions also results in an enhanced productive HIV-1 infection in the MT-4 cell cultures.

Identification and cloning of an aspartyl proteinase from Coccidioides immitis.

A 45 kDa protein was isolated from a soluble vaccine prepared from formaldehyde-killed spherules of Coccidioides immitis. From the N-terminal amino acid sequence, the protein yielded a 17-amino-acid peptide that was homologous to sequences of other fungal aspartyl proteinases. The coccidioidal cDNA encoding the proteinase was amplified using oligonucleotide primers designed from the 45 kDa N-terminal amino acid sequence and a fungal aspartyl proteinase consensus amino acid sequence. The PCR product was cloned and sequenced, and the remaining 5' upstream and 3' downstream cDNA was amplified, cloned, and sequenced. The cDNA encoding the coccidioidal aspartyl proteinase open reading frame was cloned and the fusion protein containing a C-terminal His-tag expressed in E. coli. The recombinant aspartyl proteinase was purified by immobilized metal affinity chromatography. This recombinant protein will be used for further studies to evaluate its antigenicity, including protective immunogenicity.

Characterization of factor H-related cell membrane molecules expressed by human B lymphocytes and neutrophil granulocytes.

The human factor H protein family comprises six plasma glycoproteins. Earlier we described a membranal factor H-related (mFHR) molecule that is expressed by human B lymphoblastoid cell lines and exerts cofactor activity. In our present study we screened human blood cells for the presence of mFHR proteins and further characterized these molecules. By cytofluorimetry it is shown that the factor H-specific rabbit antiserum reacts strongly with B cells and neutrophil granulocytes, but not with T cells and monocytes. On B lymphocytes mFHR is shown to be down-regulated upon activation of the cells via sIg. In experiments studying which short consensus repeat (SCR) domains are part of the cell membrane proteins we found that antibodies raised against SCRs 1-4, 19-20 and FHR-3 bound to neutrophils but not to B cells. While mFHRs derived both from B cells and granulocytes are shown to bind heparin, their size and structure are different as revealed by Western blotting. A further characteristic of the granulocyte-derived mFHR is its sensitivity to the PI-specific PLCgamma enzyme. These data demonstrate the existence of new members of the FHR protein family, as two distinct, membranal forms are identified. Based on the differences, the B cell derived molecule is termed mFHR-1 and the neutrophil derived protein mFHR-2.

[Questions of habilitation-rehabilitation in diabetes mellitus]. / A habilitáció-rehabilitáció kérdései diabetes mellitusban.

As a result of the up to date treatment the life quality of diabetic patients is improved, their life span is prolonged. The authors recite the guidelines of vocational guidance and disability evaluation of diabetics. It is generally accepted that patients treated by diet alone may choose any profession, their lifestyle need not differ from that of healthy people. Well educated diabetic patients on oral antidiabetics or insulin, who have near normoglycemic blood sugar levels, can follow the lifestyle of a healthy individual; yet they should avoid occupations where their own or others lives might be put in danger. The authors recite effective departmental orders about the questions that influence the lives of diabetic patients-for example drivers licence, sports facilities for diabetics- and are the most frequently encountered by experts. Problems of rehabilitation that arise during the management of diabetics are also discussed.