Question

How are T-dependent antigens different from T-independent antigens?

a. T-dependent antigens are most commonly bacterial flagella
b. T-dependent antigens are most commonly bacterial lipopolysaccharide (LPS)
c. T-dependent antigens have more repetitive epitopes
d. T-dependent antigens lack large, repetitive epitopes

Answer 1

T-dependent antigens require T-cell help and are often protein antigens, while T-independent antigens can activate B cells without T-cell help and are often polysaccharides or lipopolysaccharides option (b) with repetitive epitopes.

Step-by-step explanation:

T-dependent antigens differ from T-independent antigens mainly in their requirement for T cells help to activate B cells. T-dependent antigens are typically protein antigens that require processing and presentation by B cells to T cells in conjunction with MHC class II molecules which leads to B cell activation via cytokines secreted by Th2 cells.

In contrast, T-independent antigens such as polysaccharides, lipopolysaccharides (LPS), and other nonprotein molecules can activate B cells without the need for T-cell involvement. This is due to their repetitive epitopes that allow these antigens to cross-link B cell receptors directly, providing a strong sufficient activation signal without T cell help.