A Monoclonal Antibody Against an Activation Epitope on Mouse Integrin Chain β1Blocks Adhesion of Lymphocytes to the Endothelial Integrin α6β1

• Published in: Proceedings of the National Academy of Sciences - PNAS 1993-10, Vol.90 (19), p.9051-9055
• Main Authors: LENTER, M, UHLIG, H, HAMANN, A, JENÖ, P, IMHOF, B, VESTWEBER, D
• Format: Article
• Language: English
• Subjects: Antibodies; Antigens; Biological and medical sciences; Cell adhesion; Cell interactions, adhesion; Cell lines; Endothelial cells; Epitopes; Fundamental and applied biological sciences. Psychology; Integrins; Lymphocytes; Lymphoma; Molecular and cellular biology; T lymphocytes
• ISSN: 0027-8424; 1091-6490

We have generated a monoclonal antibody (mAb), 9EG7, against mouse endothelial cells that blocks adhesion of lymphocytes to endothelial cells. Sequencing of four tryptic peptides of the purified antigen revealed its identity with the integrin chain β1. The only β1integrin that is known to mediate cell-cell adhesion is α4β1(VLA-4). This is not the integrin that is functionally defined by the mAb 9EG7 on endothelial cells. First, α4is not present on the analyzed endothelial cells. Second, mAb 9EG7 does not block the cell-adhesion function of α4β1on the nonactivated mouse lymphoma L1-2. Thus, the mAb 9EG7 can functionally distinguish between different β1integrins and defines a β1integrin other than α4β1as a newly discovered cell-cell adhesion molecule. This integrin is most likely α6β1, since an antibody against the α6chain blocks lymphocyte adhesion to the same degree as the mAb 9EG7, the effect of both antibodies is not additive, and the α6chain is coprecipitated with β1in 9EG7 immunoprecipitations. Surprisingly, activation of α4β1on L1-2 cells with phorbol ester or Mn2+allows blocking of α4β1-mediated adhesion of L1-2 cells to endothelial cells with mAb 9EG7. Furthermore, only the activated α4β1heterodimer, but not the unactivated complex, is detectable with 9EG7 in immunoprecipitations and by flow cytometry. Thus, mAb 9EG7 defines an epitope on integrin chain β1, which is accessible on the α4β1heterodimer only after activation of this integrin.