PATHOLOGY

Detailed explanation-1: -Consistent with their role as critical costimulatory molecules in the initial steps of T cell activation, CD80/86 are expressed on antigen-presenting cells (APCs), such as IDCs, GCDCs, Langerhans cells and activated monocytes. The expression of these molecules can be induced upon activation of other APCs.

Detailed explanation-2: -CD80 and CD86 are upregulated on mature antigen-presenting cells (APCs) and bind to CD28 on the T cell, transducing a crucial second signal for T-cell activation along with the T-cell receptor (7).

Detailed explanation-3: -The CD28 molecule, a disulfide-linked homodimer expressed on peripheral T cells and thymocytes, mediates an essential costimulatory signal following engagement of the T cell receptor (TCR).

Detailed explanation-4: -Thus, the presence of CD28 on the T cells allowed these cells to absorb both Ld and B7-1, presumably in the form of membrane vesicles containing these two molecules.