Question:
Which is the antigen that forms loose and cotton wooly clumps during agglutination?

Correct Answer: H Antigen

Rationale:

• H antigen (Flagellar antigen) is found on the flagella of bacteria.
It is protein-based in nature and forms loose, cotton wooly clumps during agglutination.

• O antigen (Somatic antigen) is sugar-based and forms tight, granular clumps.

• F antigen is attached to fimbriae.

• D antigen is an RBC surface antigen (part of the Rh system) and does not form cotton wooly clumping.

👉 So, the characteristic of H antigen is that it forms loose and cotton wooly clumps in agglutination.

Question:
Which cells destroy virus-infected cells in innate immunity?

✅ Correct Answer: NK-cells (Natural Killer Cells)

Rationale:

• NK-cells (Natural Killer Cells) are part of innate immunity.
They directly destroy virus-infected and tumor cells without any prior exposure or antibodies.

• Macrophages engulf pathogens primarily by phagocytosis.

• Neutrophils are important in acute inflammation and bacterial infections.

• T-cells are part of adaptive (specific) immunity, not innate immunity.

👉 Therefore, NK-cells are the main cells of innate immunity in destroying virus-infected cells.