Which molecules belong to the Ig superfamily?

The immunoglobulin (Ig) superfamily is a large group of proteins that share a common structural motif characterized by the presence of immunoglobulin-like domains. This group includes a wide variety of molecules involved in immune responses, cell adhesion, and signaling.

The first choice includes T cell receptors (TCR), major histocompatibility complex (MHC) molecules, and the co-receptors CD4 and CD8. All of these play crucial roles in T cell activation and recognition of antigens, and they are indeed part of the Ig superfamily due to their structural similarities.

The second choice covers CD19, B7-1, and B7-2. CD19 is a marker on B cells that is important for signaling, while B7-1 (CD80) and B7-2 (CD86) are crucial for the co-stimulatory signals required for T cell activation. These molecules also share features that align them with the Ig superfamily.

The third choice lists Fc receptors, killer immunoglobulin-like receptors (KIR), and vascular cell adhesion molecule-1 (VCAM-1). Fc receptors bind to the Fc portion of antibodies and play roles in various immune processes, while KIR are involved in the