Examples of MALT include

• A. Thymus, spleen, bone marrow
• B. Lymph nodes, spleen, bone marrow
• C. Tonsils, lymph nodes, thymus
• D. Peyer's patches, appendix, tonsils

Answer: (D)

MALT stands for mucosa-associated lymphoid tissue, which sits at mucosal surfaces to sample antigens that enter the body through the gut, airway, and other mucosal linings. These tissues actively participate in local immune responses, especially producing IgA to help neutralize invaders at the entry points.

The classic examples are Peyer’s patches in the ileum, the appendix, and the tonsils. They are embedded in mucosal linings and organized to encounter antigens right where they'd first be encountered by the immune system. In contrast, thymus is where T cells mature (a primary lymphoid organ), and the spleen and bone marrow are systemic secondary organs not specific to mucosal surfaces. Lymph nodes are secondary lymphoid organs that filter lymph, not mucosa-specific tissue. Together, Peyer’s patches, appendix, and tonsils illustrate the mucosa-associated lymphoid system.