Cell adhesion mediated by CD4 and MHC class II proteins requires active cellular processes

Area of Science:

• Immunology
• Cell Biology

Background:

• CD4 is a cell surface accessory molecule on T lymphocytes.
• Previous work demonstrated CD4's role as an adhesion molecule binding to MHC class II on B lymphocytes.

Purpose of the Study:

• To confirm and further characterize the adhesion between human CD4 and human MHC class II molecules.
• To investigate the cellular and molecular requirements for CD4/MHC class II-mediated adhesion.

Main Methods:

• Utilized Chinese hamster ovary cells stably transfected with human CD4.
• Co-cultured these cells with human B lymphoblastoid cell lines expressing MHC class II.
• Assessed cell adhesion using microscopy and measured its dependence on temperature, ATP, and cytoskeletal integrity.

Main Results:

• Confirmed stable adhesion between CD4-transfected cells and B cells expressing MHC class II.
• Adhesion is an energy-dependent process, requiring 37°C and ATP.
• Cytoskeletal inhibitors (colchicine, cytochalasin-D, nocodazole) disrupt CD4/MHC class II adhesion.
• CD4 engagement with MHC class II induces B cell clustering, potentially via lymphocyte function-associated antigen-1 (LFA-1) activation.

Conclusions:

• CD4-MHC class II interaction is a significant adhesion mechanism between T and B lymphocytes.
• This adhesion is regulated by cellular energy and cytoskeletal dynamics.
• CD4/MHC class II engagement may influence T cell adhesion and activation through LFA-1.