Question

The term ‘MALT’ in the immune system includes?
A. Secondary lymphoid tissues or peripheral lymphoid tissues
B. Primary and secondary lymphoid tissues
C. Lymphatic nodules in the intestines, appendix and caecum
D. Lymph nodes present in the joints

Answer 1

MALT means mucosal associated lymphoid tissues. They are the site of immune response against the pathogens that enter through the mucosal surfaces of our body which are characterised by the presence of mucosal fluid. These include eyes, nose, mouth, stomach, ureter and urethra.

Complete answer:
Mucosal associated lymphoid tissues are a diffuse system which consists of small lymphoid organs that are found in different sub-mucosal sites of the body like the lungs, thyroid, gastrointestinal tract, eyes, nasopharynx, breasts, skin, and salivary glands. These tissues are populated with lymphocytes (B-lymphocytes, T-lymphocytes), macrophages and plasma cells. All these cells help to trap foreign bodies that cross the mucosal epithelium. They make up 50% of the lymphoid tissues of the body.
Depending on their locations they are divided into –
- SALT – Skin associated lymphoid tissues
- NALT – Nasal associated lymphoid tissues
- GALT – Gut associated lymphoid tissues
- CALT – Conjunctivitis associated lymphoid tissues
- BALT – Bronchus associated lymphoid tissues
- VALT – Vulva associated lymphoid tissue and
- TALT – Testis associated lymphoid tissues
Thus, the right option is A.

Additional information:
- Some inductive sites are present in the MALT where the sampling of antigen occurs and the immune response is being initiated. These inductive sites are present at different locations but all of them have the same composition of – follicles, subepithelial dome regions, interfollicles and follicle associated epithelium.
- The morphology of MALT changes with mutation and aging due to which their immune response also declines.

Note: Peyer’s patches are found in the Gut associated lymphoid tissues of the small intestine and are present in abundant amounts in the ileum. These patches have multi-fenestrated cells or M-cells which are specialised cells present in their epithelium and their function is to sample the antigens from lumen.