Integrins of the beta1 family influence keratinocyte-lymphocyte interaction.

Data from the literature indicate that ICAM-1 molecules play an important role in keratinocyte interactions with lymphocytes via the lymphocyte function-associated-1 lymphocyte-adhesion molecule. We examined the role of beta1 integrins in keratinocyte-lymphocyte adhesion under different activation conditions. Among the beta1 integrins expressed on keratinocytes and lymphocytes detected by indirect immunofluorescence microscopy and flow cytofluorometry, primarily the alpha2 and the alpha3 subunits on both cell types were involved in keratinocyte-lymphocyte adhesion. Moreover, the highest adhesion level was observed when both cell types were activated by IFN-gamma for keratinocytes and phorbol 12-myristate 13-acetate for lymphocytes, suggesting that the former involved the protein kinase C pathway. Keratinocyte activation, characterized by the expression of ICAM-1, a decrease of beta1 integrins, and the absence of alpha5beta1 integrin, was required for optimal lymphocyte adhesion. Thus, beta1 integrins remaining at the surface of IFN-gamma-treated keratinocytes could be activated by this cytokine, and could synergize with ICAM-1 and lymphocyte function-associated-1 molecules to consolidate keratinocyte-lymphocyte adhesion.

Activity of proximal promoter of the human beta(1)-integrin gene was increased in Sézary syndrome.

Changes in beta1-integrin expression have been involved in abnormal cellular interactions between malignant lymphocytes from Sézary (Sz) patients and keratinocytes. In this paper, we compare the activity of both distal and proximal promoters of the beta1-integrin gene in malignant lymphocytes from Sz patients with human normal lymphocytes. Activity of both beta1-integrin promoters was also analysed in human normal keratinocytes. Northern blot analysis shows that beta1-integrin mRNA expression is higher in malignant Sz lymphocytes than in normal lymphocytes. CAT assays show that the activity of proximal beta1-integrin promoter is markedly increased (up to 6-fold) in malignant lymphocytes from Sz patients, in comparison to normal lymphocytes. These results suggest that changes in activity of the proximal promoter of beta1-integrin subunit could be, in part, responsible for the abnormal cellular interactions between malignant lymphocytes and keratinocytes observed in Sz syndrome.

T lymphocytes from Sézary syndrome patients express beta1 integrins whose beta(1-6)-branched N-linked oligosaccharides reflect their adhesive capacity.

Sézary syndrome (Sz), characterized by slowly progressing clonal proliferation of CD4+, CD45 RO+ T cells, has several forms that are distinguished according to the epidermotropic properties of the pathological cells. In a recent paper (Derappe C, Haentjens G, Lemaire S, Feugeas JP, Lebbe C, Pasqualetto V, Bussel A, Aubery M, Néel D. Leukemia 1996;10:138), we observed that T lymphocytes from most of the Sézary patients [Szbeta(1-6)+] expressed high levels of beta(1-6)-GlcNAc-branched N-linked oligosaccharides while T lymphocytes from other patients [Szbeta(1-6)-] did not. Because this observation suggests the possibility of two forms of Sz, distinguished according to the expression rate of these glycans, we looked for a possible relationship between this expression rate and T-cell adhesiveness. Using an original protocol (Braut-Boucher F, Pichon J, Rat P, Adolphe M, Aubery M, Font J. J Immunol Methods 1995;178:41), we observed that T lymphocytes obtained from the Szbeta(1-6)+ patients adhered less to normal keratinocyte monolayers than T lymphocytes from Szbeta(1-6)- patients and normal donors. As assessed by FACS analysis, all the integrin-subunits studied were more expressed on Szbeta(1-6)-, especially alpha4, alpha5, beta1 and beta2, than on Szbeta(1-6)+ and normal lymphocytes. Although these results suggest that beta1- and beta2-integrin expression is involved in the adhesive properties of these T-cells, other factors, such as glycosylation, may also contribute. To demonstrate this possibility, we sought the presence of beta(1-6)-GlcNAc-branched N-linked oligosaccharides on beta1 integrins expressed by T lymphocytes from Sz patients. Immunoblot experiments, performed using the specific lectin from Phaseolus vulgaris (Leukoagglutinin form), showed that only the beta1 integrin subunit expressed by T lymphocytes from Szbeta(1-6)+ patients carried these glycans, supporting the concept of the involvement of T-cell glycosylation in the evolution of Sz.

The transcription factor Bright associates with Bruton's tyrosine kinase, the defective protein in immunodeficiency disease.

Binding of the transcription factor Bright to Ig heavy chain loci after B cell activation is associated with increased heavy chain transcription. We now report that Bright coprecipitates with Bruton's tyrosine kinase (Btk), the defective enzyme in X-linked immunodeficiency disease (xid). Furthermore, we observed Btk in the nucleus of activated murine B cells, and mobility shift assays suggest that it is a component of the Bright DNA-binding complex. While BRIGHT protein was synthesized in activated spleen cells from xid mice, it did not bind DNA or associate stably with Btk. These data suggest that deficiencies in BRIGHT DNA-binding activity may contribute to the defects in Ig production seen in xid mice.