CD11/CD18 (LFA-1), Human, mAb 24

The monoclonal antibody 24 recognizes an epitope of 174 kD present on leukocyte integrins, CD11/CD18 (LFA-1)
or beta 2-type integrins. The leukocyte integrins are a family of heterodimeric receptors that mediate
divalent cation-dependent cellular adhesion reactions. T cells use integrins in essentially all of their
functions. Integrins become active following signalling through other membrane receptors, which cause
both affinity alteration and an increase in integrin clustering. The monoclonal antibody 24 recognizes a
structural feature and is strictly dependent upon the presence of Mg2+. The epitope is located within, or in
close proximity to, the three conserved cation binding domains and therefore a measure of Mg2+ bound to
the leukocyte integrins and thus reflects functionally active molecules. The epitope can be induced on
polymorphonuclear leukocytes and on monocytes. Glu173 and Glu175 of the beta(2) I domain are identified
as critical for antibody 24 binding.
The monoclonal antibody 24 inhibits monocyte-dependent, antigen specific T cell proliferation and IL-2-
activated natural killer cell assays. The antibody does not interfere with mitogen-stimulated T cell
proliferation. Furthermore the monoclonal antibody 24 prevents “deadhesion” of receptor/ligand pairs,
possible locking leukocyte integrins in an “active” conformation.