Association of CD2 and T200 (CD45) in mouse T lymphocytes

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Abstract
A monoclonal antibody (mAb 12–15) reactive with the mouse CD2 was found to co-precipltate a hlgh-molecular-welght glycoprotein from mouse thymocyte, splenic lymphocyte, Con A blast, and T cell tumor detergent lysates which was identified as the leukocyte common T 200 glycoprotein (CD45). The reactivity was specific for CD2 since antibodies to CD3 did not co-precipltate the T200 glycoprotein. mAb 12–15 did not react with Immunoaffinity-purified T200 glycoprotein, ruling out the possibility that the antibody detected a cross-reactive epitope. Biochemical data Indicated that the association of CD2 with T200 was not generated during lysis of the cell and that the molecular complex was non-covalently linked since It could be destroyed by high salt washing or boiling in SDS. Distribution analysis in Triton X114-H2O revealed that, in contrast to free T200 molecules, the complexed T200 was enriched in the detergents phase. To investigate the CD2-T200 association In more detail at the cell surface, modulation of CD2 and T200 was studied. Modulation could be induced on Con A blasts by monoclonal antibodies followed by cross-linking with a FITC-conjugated second antibody. Within 24 h the expression of CD2 or T200 was reduced to ∼10–20% of the Initial value on the majority of cells. However, two-color fluorescence showed that modulation of CD2 did not lead to co-modulation of CD3 or T200. A possible physiological role of CD2-T200 complexes Is discussed.