Anti-Human CD18/CR3 (Clone KIM127) – FITC

This Fluorescein (FITC) conjugate is formulated in 0.01 M phosphate buffered saline (150 mM NaCl) PBS pH 7.4, 1% BSA and 0.09% sodium azide as a preservative.

This Fluorescein conjugate is stable when stored at 2-8°C. Do not freeze.

Next Day Ambient

Blue Laser (490 nm)

Anti-CD18/CR3 antibody (clone KIM127) recognizes an epitope on the leukocytic cell-adhesion molecule (Leu-CAM) common β chain, CD18. As such, this antigen is considered part of the Leu-CAM β integrin family of adhesion molecules. Activity is directed against immunoprecipitated human CR3 and lymphocytes expressing LFA-1. KIM127 binds to pre-activated integrins.

Integrins are a large family of α/β heterodimeric transmembrane molecules that mediate adhesion, migration, cell survival, and cell differentiation¹. The leukocytic cell-adhesion molecule (Leu-CAM) family has three members, LFA-1 (CD18/CD11a), CR3 (CD18/CD11b), and p150,95 (CD18/CD11c), all of which share the β chain CD18².

KIM127 recognizes a temperature sensitive epitope on CD18, binding to lymphocytes that express LFA-1 as well as to immunopurified CR3³. KIM127 promotes LFA-1 and CR3-dependent adhesion events and enhances aggregation of the human B lymphoblastoid line JY and human T cell line MOLT-4. This aggregation is completely blocked by anti-LFA-1 antibody DA36. KIM127 is not associated with increased surface expression of CR3 or LFA-1.

KIM127 recognizes residues Gly 504, Leu 506, and Tyr 508 of CD18 in a cysteine-rich repeat located in the long loop protruding from the C-terminal end of the integrin-epidermal growth factor-like (I-EGF) 2 domain^4,5,6. The epitope is near the extreme bend (genu) between the integrin headpiece and stalk, buried deep in the crevice formed by the bend between the α subunit thigh and calf-1 domains, and is only accessible when the integrin is extended in its activated conformation⁶. In resting integrins, the KIM127 epitope is shielded by the ⍺ subunit⁵. KIM127 preferentially reacts with activated β₂ integrins and free β₂ subunit compared with resting β₂ integrins. A switchblade-like action that extends the headpiece of the integrin away from the plasma membrane is thought to expose the KIM127 epitope when activated⁶.

Activation of LFA-1 ligand binding by Mn²⁺, and to a lesser degree by Mg²⁺ in the absence of Ca²⁺, is positively correlated with increased expression of the KIM127 epitope⁵. PMA also induces a small but consistent increase in KIM127 expression.

KIM127 was obtained from a BALB/c mouse immunized with CR3 immunopurified from a human white cell lysate³. Hybridoma lines were created by fusing spleen cells with Sp2/0 cells and screening by ELISA for their ability to bind to immunopurified CR3 and then for their ability to promote aggregation of different cell types. Mildly denaturing conditions are required during Western blotting because boiling the sample destroys the KIM127 epitope.

Members of the Leu-CAM β integrin family of adhesion molecules are widely distributed on circulating leukocytes.

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