Practice question

Question

Following are the statements which explain why patients with a-linked hyper-lgM syndrome express normal genes for other antibody subtypes but fail to produce lgG, lgA, or lgE: A. CD40 expressed on B cells is defective B. CD40L mediates binding of B-cells to T-cells and sends co-stimulatory signals to the B-cells for class switching C. Without CD40 on macrophage, class switching does not occur D. CD40L mediates binding of B-cells to macrophages and sends co-stimulatory signals to the B-cells for class switching. Select the option with correct combination.