Question

Which of the following T cell independent antigen acts through?

• A. T-cell
• B. B-cell
• C. Macrophages
• D. CD8+ T cells

Hint:

The label says no T cell help is needed, so they must trigger the antibody maker directly.

Answer 1

The Correct Option is B

Step 1: Antigens are divided into T cell dependent and T cell independent types based on whether they need helper T cell support to trigger an antibody response.

Step 2: T cell independent antigens, typically large polymeric molecules with repeating units such as bacterial polysaccharides and lipopolysaccharide, can directly cross-link the surface immunoglobulin (B cell receptors) on B cells. This direct stimulation activates B cells to make antibody without needing antigen processing and presentation by antigen presenting cells or help from T cells. Therefore they act through B cells, making option b correct.

Step 3: Because they bypass T cell help, these responses are mostly IgM, show little class switching, and generate poor immunological memory. Options a and d (T cells, CD8 positive T cells) and option c (macrophages) are not the effector route for T cell independent antigens.

Step 4: Hence T cell independent antigens act directly through B cells.