Final answer:
RAG-1 and RAG-2 enzymes are involved in maturation of both B cells and T cells during V(D)J recombination. The correct answer is d. A&B. Additionally, MHC class I molecules are found on all nucleated cells, whereas MHC class II molecules are present only on professional antigen-presenting cells.
Step-by-step explanation:
The RAG-1 and RAG-2 enzymes are essential for the initiation of V(D)J recombination, a process vital for the maturation and diversification of B and T cell receptors.
These enzymes would be present in both maturing B cells and maturing T cells, as both undergo somatic recombination to create unique antigen receptors.
While B cells mature in the bone marrow, T cells mature in the thymus. It is during their maturation that B cells and T cells generate specific receptors that allow them to recognize and mount an immune response against pathogens.
RAG enzymes are not involved in the rearrangement of MHC molecules; therefore, dendritic cells, which are antigen-presenting cells, do not require RAG-1 and RAG-2 for their function.
As a side note to address the reference question, the type of antigen-presenting molecule found on all nucleated cells is MHC class I, which presents endogenous antigens to cytotoxic T lymphocytes (CTLs).
Conversely, MHC class II molecules, which present exogenous antigens, are found only on professional antigen-presenting cells like B cells, dendritic cells, and macrophages.