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R Pospisil

Publications and source records attributed to R Pospisil.

At least 19 recordsLinked to original sources
PubMed2003

Sentinel node biopsy in gastric cancer: preliminary results.

BACKGROUND: Extent of lymphadenectomy in gastric cancer is one of the still unresolved and ongoing questions. Whether extensive procedures lead to better survival remains controversial. The detection of sentinel node could become a helpful method to define the desirable extent of lymph node dissection for each particular patient. MATERIAL AND METHODS: Prospective, single-centre, clinical trial. Sentinel node is identified using vital blue dye. After performance of D2 lymphadenectomy, the pathologist minutely investigates all lymphatic nodes by histological and immunohistochemistry techniques. RESULTS: During a period of 36 months, an attempt to localise the sentinel node for biopsy was made in 22 patients. The successful rate of sentinel node detection with a good relation between metastatic involvement of the sentinel node and other nodes was 56% (13 out of 22 patients). All these patients suffered from small tumours and early stage of the disease. In large tumours and advanced stages, blue dye stained the tissue around the tumour diffusely rendering the identification of true sentinel node impossible. Fresh frozen section of the sentinel node resulted in two patients in a false negative outcome because of micrometastatic involvement. CONCLUSIONS: Sentinel node biopsy in gastric cancer using vital staining is a feasible method. Reliable results were seen in early stage of the disease. Fresh frozen section of sentinel node has probably a low sensitivity for detection of micrometastases.

Feasibility Studies↗
PubMed2000

CD5 is A potential selecting ligand for B-cell surface immunoglobulin: a possible role in maintenance and selective expansion of normal and malignant B cells.

Although the function of CD5 on B cells is unknown, previous studies suggested that CD5 interaction with V(H) framework regions of surface immunoglobulins (Igs) may contribute to survival and expansion of B cells. Here we used B-chronic lymphocytic leukemia (B-CLL) cells and transformed B-cell lines from normal and B-CLL patients to study CD5-Ig interactions. Immobilized Ig binds and permits isolation of CD5 from lysates of CD5-expressing cell lines. Immunoglobulins or Fab fragments of different V(H) families varied in their effectiveness as inhibitors of anti-CD5 staining of CLL cells, appendix and tonsil tissue sections. Human Ig also binds to purified recombinant CD5. We show here for the first time that the unconventional Ig-CD5 interaction maps to the extracellular CD5-D2 domain whereas conventional epitopes recognized by anti-CD5 antibodies are localized in the D1 domain of CD5. We propose that interactions of VH framework regions with CD5 as a ligand may maintain, select or expand normal, autoimmune or transformed B cells and also contribute to skewing of the normal V(H) repertoire.

Antibodies, Monoclonal↗
PubMed1999

[The role of Czech physicians in the etiology, clinical aspects and epidemiology of exanthematous typhus].

Typhus fever was a lethal disease of mankind. Elucidation of its origin and spread was due to more or less unscientific approaches at the time. Only in the second half of the 19th and at the beginning of the 20th century the period of a scientific approach to knowledge of its etiology, clinical aspects and epidemiology started. A great contribution was made in this respect by Czech doctors. The latter included Professor Hlava who made a series of experiments which were among the first which investigated the etiology of this disease. He may be therefore quite rightly included among one of the discoverers of the origin of typhus fever.

Czech Republic↗
PubMed1998

B-cell superantigens may play a role in B-cell development and selection in the young rabbit appendix.

In order to develop protective antibodies against a wide range of potentially infectious pathogens, the young rabbit must diversify a limited initial repertoire by somatic mechanisms (the high copy number primary repertoire). The majority of rabbit B cells produce heavy chain variable regions by rearranging the VHa allotype-encoding VH1 gene. Thus in normal rabbits the majority of serum immunoglobulins bear VHa allotype (due to VH1 FR1 and FR3 sequences). The young rabbit appendix is a site of diversification of rearranged VH genes by gene-conversion-like and somatic hypermutation mechanisms. The newly generated B cells probably undergo selection processes that involve foreign and self-antigens and superantigens. We find preferential expansion and survival of B cells in normal and VH-mutant ali/ali rabbits based on their heavy chain FR1 and FR3 sequences (VHa allotype). This selection may involve "superantigen"-like interactions with endogenous as well as exogenous ligands.

Amino Acid Sequence↗
PubMed1998

Rabbit appendix: a site of development and selection of the B cell repertoire.

As early as 1963, it was proposed that the rabbit appendix was a homologue of the chicken bursa of Fabricius (ARCHER et al. 1963). The finding that the young rabbit appendix was thymus independent contributed to the concept of central primary lymphoid tissue. Today we know that appendix is a site that generates the high copy number primary repertoire through diversification of rearranged VH genes by gene conversion-like and somatic hypermutation mechanisms. Thus the appendix of young rabbits functions as a mammalian bursal equivalent. In the appendix, newly generated B cells also undergo selection processes involving self and foreign antigens and superantigens. Preferential expansion and survival of B cells in normal and mutant ali rabbits based on FR1 and FR3 expression may involve "superantigen"-like interactions with endogenous and exogenous ligands. One endogenous ligand appears to be CD5. Additional ligands may be produced by gut flora. Further studies in the rabbit model are needed to determine the fates of emigrants from primary GALT, their sites of postulated self-renewal in the periphery, and the nature of secondary diversification in secondary germinal centers where populations of B lymphocyte memory cells may develop. These data may also be helpful in understanding how the repertoire of human B cells is formed and how this repertoire might be manipulated for clinical benefit.

Animals↗
PubMed1997

RAG1 and RAG2 in developing rabbit appendix subpopulations.

The appendix of young rabbits is a site of primary heavy chain variable region-gene diversification and B cell selection. Appendix cells from 6- to 9-wk-old rabbits were stained and sorted for surface CD43 and IgM. We found that the CD43+IgM- and double-negative CD43-IgM- cells contained RAG1 transcripts and RAG2 protein. The presence of RAG gene products in appendix raised the possibility that pro-/pre-B cells were present in young rabbit appendix. Although an early suggestion that RAG2 plays a role in variable region-gene diversification by gene conversion in chicken bursa was not supported by studies of RAG2 protein in this tissue, we produced anti-rabbit RAG2 Abs to determine whether RAG2 protein was present in rabbit appendix, where cells that recently underwent gene conversion are found. We detected RAG2 protein in the four subpopulations of rabbit appendix lymphocytes, distinguished by surface CD43 and IgM markers. The appearance of RAG gene products during different stages of B cell maturation may reflect the function of the young rabbit appendix as a site of both B cell development and diversification.

Amino Acid Sequence↗
PubMed1996

CD5 is a potential selecting ligand for B cell surface immunoglobulin framework region sequences.

In rabbits nearly all B lymphocytes express the glycoprotein CD5, in contrast to mice and humans, where only a small proportion of B cells express this molecule (Raman, C., and K.L. Knight. 1992. J. Immunol. 149:3858-3864). CD5+ B cells appear to develop early in ontogeny and be maintained throughout life by self-renewal. The function of CD5 on B cells is still unknown. We showed earlier that "positive" selection occurs during B lymphocyte development in the rabbit appendix. This selection favors B cell expressing surface immunoglobulins with VHa2 structures in the first and third framework regions (Pospisil, R., G.O. Young-Cooper, and R.G. Mage. 1995. Proc. Natl. Acad. Sci. USA. 92:6961-6965). Here we report that F(ab')2 fragments, especially those bearing VHa2 framework region determinants, specifically interact with the B cell-surface glycoprotein CD5. This interaction can be inhibited by anti-CD5 antibodies. Furthermore, immobilized F(ab')2 fragments selectively bind CD5 molecules in appendix cell lysates. Interactions of VH framework region structures with CD5 may affect maintenance and selective expansion of particular B cells and thus contribute to autostimulatory growth of autoimmune or transformed cells.

Animals↗
PubMed1995

Preferential expansion and survival of B lymphocytes based on VH framework 1 and framework 3 expression: "positive" selection in appendix of normal and VH-mutant rabbits.

B cells with a rearranged heavy-chain variable region VHa allotype-encoding VH1 gene segment predominate throughout the life of normal rabbits and appear to be the source of the majority of serum immunoglobulins, which thus bear VHa allotypes. The functional role(s) of these VH framework region (FR) allotypic structures has not been defined. We show here that B cells expressing surface immunoglobulin with VHa2 allotypic specificities are preferentially expanded and positively selected in the appendix of young rabbits. By flow cytometry, a higher proportion of a2+ B cells were progressing through the cell cycle (S/G2/M) compared to a2- B cells, most of which were in the G1/G0 phase of the cell cycle. The majority of appendix B cells in dark zones of germinal centers of normal 6-week-old rabbits were proliferating and very little apoptosis were observed. In contrast, in 6-week-old VH-mutant ali/ali rabbits, little cell proliferation and extensive apoptosis were observed. Nonetheless even in the absence of VH1, B cells with a2-like surface immunoglobulin had developed and expanded in the appendix of 11-week-old mutants. The numbers and tissue localization of B cells undergoing apoptosis then appeared similar to those found in 6-week-old normal appendix. Thus, B cells with immunoglobulin receptors lacking the VHa2 allotypic structures were less likely to undergo clonal expansion and maturation. These data suggest that "positive" selection of B lymphocytes through FR1 and FR3 VHa allotypic structures occurs during their development in the appendix.

Animals↗
PubMed1995

[1995--the year of L. Pasteur].

1995 was proclaimed by UNESCO and by the Pasteur Institute in Paris as the year of L. Pasteur. 1995 is the 100th anniversary of his death. The author of the submitted paper describes the life and work of this genius and at the same time gives an account of the most important contributions of Pasteur's research activities for natural and medical sciences. Pasteur's work is developed further not only in Pasteur's Institute in Paris but also in other research centres worldwide, incl. the Czech and Slovak Republic.

France↗
PubMed1994

Summary of workshop findings for porcine T-lymphocyte antigens.

Fifty-four mAb preselected in the first round of the first porcine CD workshop for their possible reactivity with T-lymphocyte specific antigens and/or activation antigens were further analysed in a second round. PBMC, thymocytes and nylon-wool purified T lymphocytes derived from peripheral blood, mesenteric lymph nodes and spleen served as target cells for flow cytometric analyses. For the classification of activation antigens several experiments were performed with activated, mitogen-stimulated T lymphocytes and long-term T-lymphocyte cultures. Out of the 54 mAb, 35 mAb could be distributed to six different CD clusters and two swine workshop clusters (SWC). Five mAb could be distributed to the porcine CD2, four mAb to the CD4. Six mAb seemed to recognize the porcine CD5 and two mAb the porcine CD6 analogue. Six mAb were directed against the porcine CD8, whereas two different epitopes could be defined. One mAb was directed against the porcine CD25 analogue. Nine mAb could be clustered to the SWC1, defining an antigen on T lymphocytes and cells of the myeloic linage. Two mAb with high T-cell specificity were clustered to the SWC2.

Animals↗
PubMed1994

Analysis of monoclonal antibodies reactive with the porcine CD2 antigen.

As result of the First International Swine CD Workshop, six monoclonal antibodies (mAbs) (numbers 014, 023, 024, 057, 128, and 130) clustered closely to the internal standard anti-porcine CD2 mAb, MSA4. Despite the close clustering, the cluster was split into two subgroups. To further characterize the relationship between these mAbs, they were used in flow cytometry to inhibit binding of MSA4 to porcine lymphocytes. mAbs 014 (1038-8-31), 023 (MAC83), 024 (MAC80), 057 (PG168), and 128 (MSA4) completely inhibited the binding of MSA4, mAb 130 (MSA2) failed to inhibit MSA4 binding. On dual parameter flow cytometry comparing MSA2 with MSA4, all MSA2+ cells were MSA4+, two thirds of the MSA4+ cells were MSA2-. We conclude that five of the mAbs bind to the same or a closely related epitope on porcine lymphocytes. mAb 130 appears to have aberrantly clustered with the CD2 group of mAb.

Animals↗
PubMed1994

Analysis of monoclonal antibodies reactive with the porcine CD4 antigen.

As result of the First International Swine CD Workshop, four monoclonal antibodies (mAb) (#002, 054, 118, and 127) clustered closely to the internal standard anti-porcine CD4 mAb, 74-12-4. To further characterize the relationship between these mAb, they were used in flow cytometry to inhibit binding of 74-12-4 to porcine lymphocytes. mAb #002 (74-12-4) and #054 (PT90) completely inhibited, while mAb #127 (10.2H2) and #118 (b38c6) partially inhibited (57% and 77% respectively), the binding of 74-12-4. Furthermore, none of the mAbs bound to a 74-12-4 negative strain of pigs. We conclude that the four mAb bind to the same, or a closely related, epitope on porcine lymphocytes.

Animals↗
PubMed1994

Analyses of monoclonal antibodies reactive with porcine CD5.

Among all monoclonal antibodies (mAbs) analyzed in the first porcine CD workshop, six mAbs showed reactivity to the porcine CD5 antigen (workshop mAbs 067, 068, 069, 070, 071 and 119). Because of lack of immunoprecipitation studies for five (067, 068, 069, 070 and 071) out of the six mAbs, only one mAb (119) could be definitely characterized as mAb against the monomeric 63 kDa porcine CD5 antigen. The five other mAbs included in this cluster are characterized by an identical labelling pattern in FCM and competition of the CD5 epitope recognized by mAb 119. These mAbs were allocated to the wCD5 subcluster.

Animals↗
PubMed1994

Analyses of monoclonal antibodies reactive with porcine CD6.

Amongst the monoclonal antibodies (mAbs) submitted to the first porcine CD workshop, two mAbs (workshop numbers 055 and 120) could be identified to recognize the porcine CD6 analogue. Both mAbs seemed to be highly T-cell specific and showed neither reactivity with cells of the myeloic lineage nor with B lymphocytes. The observed molecular mass of the antigen precipitated by mAb 120 of 110 kDa confirmed this classification. Without molecular analyses of the antigen recognized by mAb 055, but similar staining pattern in FCM compared with 120, mAb 055 was allocated to the wCD6 subcluster.

Animals↗
PubMed1994

Analyses of mAb reactive with porcine CD8.

Among all mAb submitted to the first porcine CD workshop, based on FCM analyses six mAb could be identified to recognize the porcine CD8 analogue (workshop Nos. 004, 051, 052, 053, 108 and 109). In immunoprecipitation studies three mAb (Nos. 004, 108 and 109) recognized an antigen with an apparent molecular mass of about 35 kDa under reducing conditions and about 70 kDa under non-reducing conditions. The molecular masses of the antigens recognized by the three other mAb (Nos. 051, 052 and 053) are still unknown. Epitope analyses performed by blocking experiments led to the determination of two CD8 epitopes: CD8a and CD8b. CD8a is recognized by mAb Nos. 004, 051 and 052, and CD8b by Nos. 053, 108 and 109.

Animals↗