Q.28 Which of the immune cells listed below are agranular?
P. Eosinophils
Q. Mast cells
R. Monocytes
S. T-cells
(A) P and Q only
(B) Q and R only
(C) R and S only
(D) S and P only

Correct Answer: (C) R and S only

Agranular immune cells lack visible cytoplasmic granules under a microscope, distinguishing them from granular leukocytes like neutrophils, eosinophils, and basophils. Monocytes and T-cells (a type of lymphocyte) fit this category, while eosinophils and mast cells contain prominent granules.​

Option Analysis

• P. Eosinophils: These are granular leukocytes with large, eosin-staining granules that combat parasites and allergies. They do not qualify as agranular.​

• Q. Mast cells: Tissue-resident cells packed with secretory granules containing histamine and heparin for allergic responses. They are distinctly granular, not agranular.​

• R. Monocytes: Agranular mononuclear leukocytes that differentiate into macrophages for phagocytosis; granules are absent or minimal.​

• S. T-cells: Lymphocytes lacking visible granules, key in adaptive immunity via antigen recognition. Agranular by definition.​

Agranular immune cells, also called agranulocytes, play vital roles in adaptive immunity without the cytoplasmic granules seen in granulocytes. Understanding agranular leukocytes like monocytes and T-cells versus granular ones like eosinophils and mast cells is key for CSIR NET Life Sciences exams. This guide breaks down their classification, functions, and a solved MCQ.​

Granular vs Agranular Leukocytes

Granulocytes (neutrophils, eosinophils, basophils) feature enzyme-filled granules for innate immunity, making up 65% of white blood cells. Agranular immune cells lack these, appearing clear under microscopy, and comprise 35%, focusing on phagocytosis and antibody production.​

• Neutrophils, eosinophils: Prominent granules for pathogen destruction.​

• Monocytes, lymphocytes (T-cells, B-cells): Minimal or no granules, mononuclear nuclei.​

Specific Cell Analysis

Eosinophils (P): Granular with bi-lobed nuclei; granules target parasites. Not agranular.​

Mast cells (Q): Granule-rich for degranulation in allergies; tissue-based, similar to basophils. Granular.​

Monocytes (R): Agranular, kidney-shaped nuclei; become macrophages for antigen presentation.​

T-cells (S): Agranular lymphocytes for cell-mediated immunity; no visible granules.​