There are number of specific T cell surface molecules involved in various functions of adaptive immune response. Column X represents a list of T cell surface molecules and Column Y with the possible functional characteristics: Column X Column Y A. T cell receptor (i) binds to CD40 on B cells and APCs and triggers activation of APCs and activation/differentiation of B cells. B. CD28 (ii) binds to MHC class I molecules and restricts I cytotoxic cells to recognizing only peptide presented on MHC class I C. CD8 (iii) binds to B7 - 1, 2 or CD80/86 on B cells and APCs, which triggers T cell activation. D. CD154 (iv) consists of two poly-peptide chains α and β and some consist of poly-peptide chains γ and δ. Which of the following option has all correct matches?
T cell surface molecules and Functions
T cells are key players in the adaptive immune response. Their surface molecules are critical for recognizing antigens, receiving co-stimulatory signals, and interacting with other immune cells like B cells and Antigen-Presenting Cells (APCs). Matching these molecules to their specific roles is fundamental to understanding T cell function.
Let's analyze the function of each T cell surface molecule listed:
| Column X (T cell surface molecule) | Column Y (Functional characteristics) |
|---|---|
| A. T cell receptor | (i) binds to CD40 on B cells and APCs and triggers activation of APCs and activation/differentiation of B cells. |
| B. CD28 | (ii) binds to MHC class I molecules and restricts I cytotoxic cells to recognizing only peptide presented on MHC class I. |
| C. CD8 | (iii) binds to B7 - 1, 2 or CD80/86 on B cells and APCs, which triggers T cell activation. |
| D. CD154 | (iv) consists of two poly-peptide chains $\alpha$ and $\beta$ and some consist of poly-peptide chains $\gamma$ and $\delta$. |
Now, let's match each molecule in Column X with its correct function in Column Y:
- A. T cell receptor (TCR): The T cell receptor is the primary molecule responsible for recognizing specific antigens presented by MHC molecules. Its structure is well-defined. The most common form consists of alpha ($\alpha$) and beta ($\beta$) polypeptide chains. A less common form consists of gamma ($\gamma$) and delta ($\delta$) chains. This description perfectly matches characteristic (iv). Therefore, A - (iv) is the correct match.
- B. CD28: CD28 is a co-stimulatory molecule found on T cells. It is essential for full T cell activation. It binds to B7-1 (CD80) and B7-2 (CD86) molecules, which are typically expressed on professional APCs like dendritic cells, macrophages, and activated B cells. This interaction provides the second signal needed for T cell activation, preventing anergy. This function aligns with characteristic (iii). Therefore, B - (iii) is the correct match.
- C. CD8: CD8 is a co-receptor found on cytotoxic T lymphocytes (CTLs). It binds to the non-polymorphic $\alpha$3 domain of MHC class I molecules. This interaction helps stabilize the binding between the T cell and the target cell and contributes to the signaling cascade. CD8+ T cells (CTLs) recognize antigens presented on MHC class I, which are typically found on most nucleated cells and are involved in presenting peptides derived from intracellular pathogens. This function is described in characteristic (ii). Therefore, C - (ii) is the correct match.
- D. CD154: CD154, also known as CD40 Ligand (CD40L), is a molecule expressed on activated T cells, particularly helper T cells. It plays a crucial role in T-dependent B cell activation and differentiation, as well as activating APCs. CD154 binds to CD40, a receptor found on B cells, macrophages, dendritic cells, and other APCs. The interaction between CD154 on the T cell and CD40 on the B cell is vital for initiating germinal center reactions, antibody class switching, and somatic hypermutation. The interaction with CD40 on APCs enhances their ability to activate T cells. This function is described in characteristic (i). Therefore, D - (i) is the correct match.
Based on these analyses, the correct matches are A - (iv), B - (iii), C - (ii), and D - (i).
Important Questions from Immune System
- Which of the following is correct about the impact of stress on immune system of an individual?
- Which components of psychoneuro immunological system is not effected by glucocorticoids
- Brief stress enhances the activity of immune system as evidenced by the action of
- Choose the correct sequence of response of immune system
A. Synthesizes antibodies which comprises immunoglobulins
B. Immune system identifies foreign substances in the body
C. Immunoglobulins specifically designed to bind the antigens
D. Destroy the antigens
Choose the correct answer from the options given below: Which one of the following influenza A virus subtypes caused severe avian flu and was responsible for disease outbreak in the year 1997 in Hong Kong?
