Search PubMed⌕ Search

Biomedical subjects

S Jalkanen

Publications and source records attributed to S Jalkanen.

At least 91 records · Page 5Linked to original sources
PubMed1993

Chicken B cells adhere to the CS-1 site of fibronectin throughout their bursal and postbursal development.

In chickens, the pre-B cell development takes place in a specialized organ, the bursa of Fabricius. In this study, we show that fibronectin can be detected in the bursa at least from the day 15 of embryonic incubation up to 10 weeks of age after which the bursa starts to involute. During the embryonic incubation, fibronectin localizes mainly in the areas between the follicles and later on also in the border zone between the cortical and medullary parts of the lymphoid follicles. By adhesion studies with synthetic peptides we show that immature bursal B cells bind in a dose-dependent manner to the CS-1 site of the type III connecting segment at the carboxy-terminal end of fibronectin throughout their bursal development. Postbursal B cells from chicken spleen also display a similar preference of binding to the CS-1 site of fibronectin, whereas peripheral blood B lymphocytes bind to the 40-kDa fragment of fibronectin, but do not adhere as strongly to the CS-1 site. Instead, they recognize to some extent also the heparin-binding YEKPGSPPREVVPRPRPGV peptide. The adhesion of the bursal B cells to the CS-1 site can partially be blocked by preincubation of cells with a synthetic CS-1 peptide and also by preincubation with a monoclonal anti-fibronectin receptor antibody. In contrast, the RGD motif present in several adhesion-associated stromal molecules did not promote any adherence of bursal lymphocytes. The bursal B cells which adhere to the fibronectin molecule in vitro form only a small fraction of the total number of B cells present in the bursa as only less than 4% of the cells remained bound to the surface coated with fibronectin in the adhesion studies. In conclusion, these results suggest that fibronectin may be involved in the differentiation of pre-B cells in the bursa of Fabricius and also in the adherence of postbursal B cells in the spleen.

Amino Acid Sequence↗
PubMed1993

Lymphocyte homing receptor (CD44) expression is associated with poor prognosis in gastrointestinal lymphoma.

Lymphocyte homing receptor (CD44) is involved in lymphocyte adhesion to endothelial cells of high endothelial venules (HEVs) and lymphocyte exit from the blood circulation, and it may be involved also in hematogenous dissemination of malignant lymphoma. Prognostic significance of lymphocyte homing receptor expression defined by Hermes-3 antibody was studied among 27 gastrointestinal lymphomas followed up for 8 to 20 years after the diagnosis. Lymphomas lacking or with very weak homing receptor expression (n = 14, 52%) were associated with 57% 10-year survival rate as compared with only 15% among lymphomas that expressed CD44 more strongly (P = 0.02). We conclude that lack of lymphocyte homing receptor expression is common in gastrointestinal lymphoma, and that CD44 expression is associated with unfavourable prognosis.

Adult↗
PubMed1993

Regulated expression of exon v6 containing isoforms of CD44 in man: downregulation during malignant transformation of tumors of squamocellular origin.

CD44 is a family of glycoproteins involved in cell-cell and cell-matrix interactions. In addition to the major 90-kD form present on most hematopoietic cells, larger 140-230 kD forms are found on keratinocytes and carcinoma cell lines. These bigger isoforms of CD44 arise by alternative splicing that results in insertion of one or more of the "variant" exons into the extracellular part of the 90-kD constant form of the molecule. In rat, v6 (variant exon v6) containing form of CD44 confers metastatic potential to carcinoma cells, and therefore, it is of interest to study the distribution of this isoform in humans. We raised antibodies against a synthetic peptide containing a sequence encoded by the exon v6. A mAb thus obtained (designated Var3.1) strongly reacted with the plasma membranes of squamous cells in upper layers of skin and tonsil surface epithelia. Weaker staining was seen in germinal centers, vascular endothelia and enterocytes. Exon v6 containing forms of CD44 (CD44v6) were absent from tissue leukocytes and connective tissue components. In comparison, Hermes-3 epitope (on the constant part) containing forms of CD44 were preferentially localized in basal layers of epithelia, present on the surface on most leukocytes and connective tissue cells, and undetectable on the luminal surface of high endothelial venules. In benign neoplasms, epithelial cells stained with mAb Var3.1 like in normal tissues. In contrast, immunostaining of 30 squamous carcinoma specimens (both primary and metastatic lesions) revealed that malignant transformation resulted in downregulation or disappearance of Var3.1 epitope, but in majority of cases, not in diminished synthesis of the Hermes-3 epitope. Biochemical analyses showed that mAb Var3.1 recognized two major forms of CD44 (220 and 300 kD). In conclusion, epitopes on exon v6 and constant part of CD44 are differentially synthesized and regulated during normal and malignant growth of cells in man.

Adult↗
PubMed1993

Yersinia lipopolysaccharide is modified by human monocytes.

Reactive arthritis is usually self-limiting polyarthritis, which develops after certain gastrointestinal or urogenital tract infections, mostly in susceptible HLA B27-positive individuals. In the pathogenesis of this arthritis, it is probably important that structures of the causative bacteria are found in the affected joints. The structure found in the synovial fluid phagocytes of the patients with reactive arthritis after Yersinia, Salmonella, and Shigella infections has always been lipopolysaccharide (LPS) of the causative bacteria. It has been in a highly processed form but still immunoreactive. To follow the degradation process of LPS, we fed peripheral blood monocytes of healthy blood donors with heat-killed Yersinia enterocolitica O:3 bacteria in vitro and monitored the fate of LPS by immunofluorescence and immunoblotting methods. Heat-killed bacteria were used since Y. enterocolitica O:3 bacteria are able to live inside monocytes in vitro and dividing intracellular bacteria would have made it impossible to monitor the degradation process of LPS with these methods. Both the core region and the O-polysaccharide chain of LPS persisted in cytoplasmic vacuoles and on plasma membrane of monocytes through the 7-day follow-up time. Migration properties of processed LPS in sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested structural modifications of LPS. We also demonstrated that core epitopes appearing on the surface of Yersinia-fed monocytes on day 4 of incubation were processed intracellularly, suggesting that LPS-containing phagocytes are a constant source of membrane-active LPS in their microenvironment as well as in the joints of arthritic patients.

Antigens, Bacterial↗
PubMed1993

Endothelial cell-binding properties of lymphocytes infiltrated into human diabetic pancreas. Implications for pathogenesis of IDDM.

In IDDM, mononuclear cells accumulate in the islets of Langerhans and destroy insulin-producing beta-cells. To study the mechanisms that control extravasation of circulating mononuclear cells into the pancreas, we examined the phenotype of vascular endothelium of the pancreas, propagated a T-cell line from pancreatic islets at the onset of the disease and compared endothelial binding of this cell line in vitro to vascular endothelium in different body regions. The adhesion molecules expressed on the resulting T-cell line and the functional binding capacity of these cells to the endothelium of the normal and diabetic pancreas, mucosa-associated lymphatic tissues, and regional and peripheral lymph nodes were studied. We present evidence of pancreatic endothelial activation in diabetes, leading to endothelial morphology typical for HEVs and accompanying local increase in extravasation of mononuclear cells into the pancreas. Endothelial-cell binding experiments with the T-cell line showed strong adherence of the cells to the endothelium of diabetic pancreas and mucosal lymphoid tissue. The cell line was uniformly CD4-positive, TCR V beta 5.1-positive, LFA-1-positive (CD 11a/CD18), VLA-4 alpha-positive (CD 49d), and CD 44-positive but negative for L-selectin (peripheral lymph node homing receptor). The pancreatic or control cell lines showed no binding to vessels of normal pancreas, and the binding of the pancreatic cell line to the endothelium of peripheral lymph node was weak. Our results suggest that lymphocyte-endothelial cell interactions are important for the accumulation of inflammatory mononuclear cells into the pancreas and imply that lymphocytes derived from the mucosal lymphoid tissue may be involved in the pathogenesis of IDDM.

Cell Adhesion↗
PubMed1993

A novel endothelial cell molecule mediating lymphocyte binding in humans.

Leukocyte extravasation is critically dependent on proper interactions between leukocytes and vascular endothelial cells. Although several molecules mediating these interactions have been identified, all the homing phenomena observed in vivo cannot be explained on the basis of the known adhesion molecules. To discover novel molecules involved in leukocyte migration we have made monoclonal antibodies against human endothelial cells. With the help of one such monoclonal antibody a novel endothelial cell molecule called vascular adhesion protein-1 (VAP-1) was found. Uniqueness of VAP-1 is evident on the basis of its expression pattern, molecular mass, functional properties and N-terminal amino acid sequence. VAP-1 mediates lymphocyte binding to endothelium in peripheral lymph nodes, tonsil and inflamed synovium. Therefore, VAP-1 is relevant to understanding of the physiologic and pathologic lymphocyte migration in man, and may be valuable for dissecting the molecular events of tissue-selective lymphocyte homing.

Amine Oxidase (Copper-Containing)↗
PubMed1993

Glycoprotein CD44 expression and its association with survival in breast cancer.

To investigate the clinical significance of CD44 expression (lymphocyte-homing receptor) in adenocarcinoma, deparaffinized sections from 198 female breast carcinomas were stained with Hermes-3 MoAb for CD44 glycoprotein. In 16% of the cancers most (> or = 90%) of the cancer cells stained positively for CD44, whereas the rest of the cancers were either heterogenous (46%) or negative (38%) in CD44 staining. Cancers with > 50% CD44 positive cells were more often poorly differentiated (grade 3) than those with < or = 50% positive cells (38 vs. 19%, P = 0.006), they had higher mitotic counts (P = 0.04), and were more often estrogen receptor negative (52 vs. 31%, P = 0.01). Among ductal not otherwise specified cancers and node-positive cancers strong CD44 expression was associated with poor outcome (P = 0.05 and 0.02, respectively). However, CD44 expression was not an independent prognostic factor in these subgroups in a multivariate analysis. Unlike in lymphomas the unfavorable prognosis associated with CD44 expression may not be explained by the greater metastatic potential of CD44-positive cells, because the difference in mortality between the groups appeared to diminish with time, and CD44 positivity was associated with aggressive histological features.

Adenocarcinoma↗
PubMed1992

Selective endothelial binding of interleukin-2-dependent human T-cell lines derived from different tissues.

The ability of lymphocytes to recognize and bind to high endothelial venules (HEVs) is essential for lymphocyte migration from the blood into lymphoid tissues and into sites of inflammation. Endothelial cell binding capacity also critically determines the clinical usefulness of T-cell lines and clones in immunotherapy. In the present study, interleukin-2-dependent T-cell lines were derived from the blood, lamina propria of the gut, inflamed synovium, synovial fluid, and peripheral lymph nodes. After 3-8 weeks of culture, the expression of homing-associated molecules and binding to mucosal, synovial, and peripheral lymph node HEVs were analyzed. Cell lines derived from the blood and mucosal sites bound significantly better to mucosal and synovial HEVs than to peripheral lymph node HEVs. Three out of seven synovial T-cell lines showed preferential binding to synovial HEVs, whereas the rest bound almost equally well to synovial and mucosal HEVs. T-cell lines from peripheral lymph nodes bound preferentially to lymph node HEVs despite the lack of L-selectin (the peripheral lymph node homing receptor). Expression of the known homing-associated molecules did not predict the HEV-binding specificity of these lines. Importantly, two cell lines bound well to synovial venules, but poorly, if at all, to mucosal or peripheral lymph node HEVs, supporting the concept that synovial-specific HEV recognition mechanisms exist. In conclusion, the tissue origin of T-cell lines critically determines their selectivity for endothelial cell recognition, and besides the known "homing receptors," other molecules may also mediate tissue-specific HEV-binding of interleukin-2-activated T cells.

Antigens, CD↗
PubMed1992

A 90-kilodalton endothelial cell molecule mediating lymphocyte binding in humans.

Interactions between leukocyte surface receptors and their ligands on vascular endothelial cells control lymphocyte traffic between the blood and various lymphoid organs, as well as extravasation of leukocytes into sites of inflammation. A heretofore undescribed 90-kilodalton human endothelial cell adhesion molecule (VAP-1) defined by a monoclonal antibody 1B2 is described. The expression pattern, molecular mass, functional properties, and an amino-terminal amino acid sequence define VAP-1 as an endothelial ligand for lymphocytes. VAP-1 helps to elucidate the complex heterotypic cell interactions that direct tissue-selective lymphocyte migration in man.

Amine Oxidase (Copper-Containing)↗
PubMed1992

Regulation of L-selectin expression on cultured bone marrow leukocytes and their precursors.

L-selectin (LECAM-1, LAM-1, MEL-14 antigen, Dreg antigen) is one of the molecules controlling lymphocyte homing from the blood to peripheral lymph nodes and granulocyte adhesion to inflamed endothelium. In this work, regulation of L-selectin expression on mouse bone marrow cells was studied. L-selectin-negative cells were isolated by panning technique, cultured for 1-7 days with cytokines and mitogens, and L-selectin expression was analyzed by immunofluorescence staining. When cultured for 3 days with interleukin (IL) 1, IL 2, IL 5, IL 6, phytohemagglutinin, pokeweed mitogen or in the medium alone, 75%-85% of L-selectin-negative large cells (including granulocytes, macrophages/monocytes, blasts and their precursors) became L-selectin positive. In contrast, IL 3, IL 4, granulocyte-macrophage colony-stimulating factor (GM-CSF) and lipopolysaccharide (LPS) prevented the induction of L-selectin in a time- and dose-dependent manner. GM-CSF was the most potent inhibitor and only 10%-15% of cells became L-selectin positive after 3 days of culture. Furthermore, L-selectin was down-regulated on cultured unselected bone marrow cells by IL 3, IL 4, GM-CSF and LPS stimulation. After culture, the relative molecular mass of L-selectin was 100 kDa, similar to the size of the granulocyte form of this antigen. Cultured cells adhered to high endothelial venules (HEV) only 10%-32% as effectively as freshly isolated bone marrow cells despite high levels of L-selectin expression. The phenotypic analysis and the HEV binding data indicate that after culturing L-selectin was almost exclusively expressed on bone marrow leukocytes of myeloid series, and on these cells it was not functional in mediating peripheral lymph node HEV binding. Overall, these results show that the expression of L-selectin can be modulated by regulating the maturation and differentiation of the cells in vitro. This supports the idea that different cytokines and mitogens may also be important in controlling migrational status of leukocytes in vivo.

Animals↗
PubMed1992

Proliferating cell nuclear antigen (PCNA) as a prognostic factor in non-Hodgkin's lymphoma.

The prognostic value of immunoperoxidase staining for proliferating cell nuclear antigen (PCNA) was studied in a series of 140 non-Hodgkin's lymphomas with median follow-up of 9 years. Lymphomas where > 50% of cells showed positive staining for PCNA had inferior 5-year survival as compared with those with less than 50% of positive cells (57% vs 41%, P = 0.008). The presence of > 50% of positively staining cells for PCNA was strongly associated with a larger than the median size of the SPF (median, 8.3%), and high histological grade of malignancy (P < 0.0001 for both). Lymphomas with both a large percentage (> 50%) of PCNA positive cells and a larger than the median SPF had inferior outcome as compared with lymphomas where either one or both of these factors were small. Although PCNA staining was not an independent prognostic factor in a multivariate analysis, it appears to be supplementary to the SPF even if determined from old paraffin-embedded tissue material.

Adolescent↗
PubMed1992

Lymphocyte CD44 binds the COOH-terminal heparin-binding domain of fibronectin.

The lymphocyte-high endothelial venule (HEV) cell interaction is an essential element of the immune system, as it controls lymphocyte recirculation between blood and lymphoid organs in the body. This interaction involves an 85-95-kD class of lymphocyte surface glycoprotein(s), CD44. A subset of lymphocyte CD44 molecules is modified by covalent linkage to chondroitin sulfate (Jalkanen, S., M. Jalkanen, R. Bargatze, M. Tammi, and E. C. Butcher. 1988. J. Immunol. 141:1615-1623). In this work, we show that removal of chondroitin sulfate by chondroitinase treatment of lymphocytes or incubation of HEV with chondroitin sulfate does not significantly inhibit lymphocyte binding to HEV, suggesting that chondroitin sulfate is not involved in endothelial cell recognition of lymphocytes. Affinity-purified CD44 antigen was, on the other hand, observed to bind native Type I collagen fibrils, laminin, and fibronectin, but not gelatin. Binding to fibronectin was studied more closely, and it was found to be mediated through the chondroitin sulfate-containing form of the molecule. The binding site on fibronectin was the COOH-terminal heparin binding domain, because (a) the COOH-terminal heparin-binding fragment of fibronectin-bound isolated CD44 antigen; (b) chondroitin sulfate inhibited this binding; and (c) finally, the ectodomain of another cell surface proteoglycan, syndecan, which is known to bind the COOH-terminal heparin binding domain of fibronectin (Saunders, S., and M. Bernfield. 1988. J. Cell Biol. 106: 423-430), inhibited binding of CD44 both to intact fibronectin and to its heparin binding domain. Moreover, inhibition studies showed that binding of a lymphoblastoid cell line, KCA, to heparin binding peptides from COOH-terminal heparin binding fragment of fibronectin was mediated via CD44. These findings suggest that recirculating lymphocytes use the CD44 class of molecules not only for binding to HEV at the site of lymphocyte entry to lymphoid organs as reported earlier but also within the lymphatic tissue where CD44, especially the subset modified by chondroitin sulfate, is used for interaction with extracellular matrix molecules such as fibronectin.

Amino Acid Sequence↗
PubMed1992

Involvement of the avian mu heavy chain in recolonization of the bursa of Fabricius.

In the chicken, the B cells develop in a specialized organ, the bursa of Fabricius. Earlier it was shown that neonatal bursal cells treated with polyclonal anti-chicken immunoglobulin antibodies are not able to recolonize the bursa when transferred into cyclophosphamide-treated chicks. In this study, 4-day-old bursal cells were treated with different polyclonal and monoclonal anti-immunoglobulin antibodies and transferred into 4-day-old cyclophosphamide-treated chickens. Two monoclonal anti-chicken IgM antibodies, CVI-59.7 and 21-2B2, recognizing distinct epitopes of the mu heavy chain, were inhibitory. Incubation of cells with 21-2B2 antibody caused about 90% inhibition of bursal recolonization. After incubation with CVI-59.7 antibody the inhibition was 50%. The high inhibition by 21-2B2 antibody was also seen when F(ab')2 fragments of the antibody were used. These results suggest that the entry of the cells needed for bursal recolonization is inhibited almost totally by 21-2B2 antibody, or that this antibody blocks further proliferation of the cells in bursal follicles. In conclusion, we have shown that a mu heavy chain epitope is intimately involved in the recolonization of bursal follicles, and distinct epitopes of the mu heavy chain are not equally important in this process.

Animals↗
PubMed1992

Macrophages, T cell receptor usage, and endothelial cell activation in the pancreas at the onset of insulin-dependent diabetes mellitus.

Current knowledge of the phenotype of mononuclear cells accumulating in pancreatic islets in insulin-dependent diabetes (IDDM) and factors determining their homing into the pancreas is limited. Therefore, a pancreas obtained at the onset of IDDM was studied in detail. Cryostat sections were stained for mononuclear cell types, T cell receptor subtypes, and adhesion molecules of vascular endothelium and studied by immunofluorescence microscopy, and peripheral blood mononuclear cells were phenotyped using flow cytometry. Monocytes/macrophages (lysozyme- or CD 14-reactive cells) were identified among other mononuclear cell types in islet infiltrates. V beta 8-positive T cells were overrepresented, but T cells with other V beta s studied (V beta 5, V beta 5.1, V beta 6, V beta 12) were also found. The vascular endothelium of the islets and many small vessels nearby islets strongly expressed intercellular adhesion molecule-1, whereas vascular cell adhesion molecule-1 and E-selectin were totally absent. We conclude: (a) that increased expression of intercellular adhesion molecule-1 on vascular endothelium may increase endothelial adhesion of mononuclear cells and enhance their accumulation in the pancreas during diabetic insulitis; (b) that T cells with certain T cell receptors can be enriched in infiltrated pancreatic islets; and (c) that macrophages and antigen-specific CD 8-positive T cells are involved in pancreatic beta cell destruction at the onset of IDDM.

Antigens, CD↗
PubMed1991

Comparison of S-phase fraction, working formulation, and Kiel classification in non-Hodgkin's lymphoma.

The prognostic value of S-phase fraction (SPF), determined by flow cytometric study from paraffin-embedded tissue, and grading by Working Formulation (WF) and Kiel classification were compared among 245 patients with non-Hodgkin's lymphoma followed for the median of 89 months or until death. Histologic reclassification and SPF determinations were done without knowledge on clinical data. SPF (P equals 0.0001), WF (P equals 0.0003), and Kiel classification (P equals 0.0008) were associated with mortality in lymphoma in a univariate analysis, and WF and SPF were independent prognostic factors in Cox's multivariate analysis. Although SPF correlated strongly both with WF and Kiel grades (P less than 0.0001), low-grade and high-grade malignant lymphomas according to Kiel classification, and high-grade lymphomas according to WF could be divided into groups with significantly different outcome by SPF. The results suggests a role for SPF in therapeutic decision-making.

Adolescent↗