Question

TCRs possess single binding site for antigen; used only as cell surface receptors for antigen--never as soluble Ag-binding molecule

Answer 1

TCRs, or T-Cell Receptors, possess a single antigen-binding site and are always associated with the T cell membrane, whereas B-cell Receptors (BCRs) can bind directly to antigens and have two antigen-binding sites. TCRs interact with antigens that are presented on MHC molecules, while BCRs can recognize various molecular classes.

Step-by-step explanation:

T-Cell Receptors (TCRs)

TCRs, or T-Cell Receptors, are pivotal in the immune system for the recognition of specific antigens. Unlike antibodies, TCRs are never found as soluble antigen-binding molecules; they are always part of the T cell membrane. TCRs consist of two peptide chains (α and β chains) that span the cytoplasmic membrane of the T cell. Each TCR has a single antigen-binding site, and this specificity is due to the variable region of the receptor, which works akin to a key in a lock when it comes to recognizing antigens.

B cells, however, use B-cell Receptors (BCRs) which can bind directly to free antigens without the need for antigen presentation by MHC molecules. BCRs are membrane-bound monomeric forms of IgD and IgM and have two identical antigen-binding sites. TCRs can only interact with protein epitopes that are presented within the antigen-binding cleft of MHC I or MHC II, while BCRs can recognize a wider variety of molecular classes.

Therefore, the fundamental difference in antigen recognition between TCRs and BCRs lies in how they interact with antigens and the forms of antigens they can recognize.

Answer 2

The statement given "TCRs possess single binding site for antigen; used only as cell surface receptors for antigen--never as soluble Ag-binding molecule" is true because TCRs possess a single binding site for antigens and are used only as cell surface receptors for antigens, never as soluble antigen-binding molecules.

Step-by-step explanation:

T-cell receptors (TCRs) are essential components of the adaptive immune system and play a central role in recognizing antigens presented by major histocompatibility complex (MHC) molecules on the surface of antigen-presenting cells. TCRs have a single binding site that interacts with specific peptide-MHC complexes.

Unlike antibodies, which can be secreted as soluble molecules, TCRs are not produced in a soluble form. Instead, they are integral membrane proteins expressed on the surface of T cells. This cell surface expression is crucial for T cells to interact with antigens presented by other cells and initiate immune responses.

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Complete Question

TCRs possess single binding site for antigen; used only as cell surface receptors for antigen--never as soluble Ag-binding molecule

True

False

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