# DBT JRF 2020 — Question 1

Exam: DBT JRF 2020 · Section: A · Topic: Immunology · Difficulty: Medium

## Question

The Freund's complete adjuvant is a mixture of

## Options

- **A.** amino acids, detergent and dried S. aureus cells
- **B.** glucose, oil, and dried E. coli cells
- **C.** oil, water, dried bacterial spores
- **D.** oil, water and dried Mycobacterium cells

## Answer

Option A

## Explanation

Freund's Complete Adjuvant (FCA) is an oil-in-water emulsion composed of mineral oil, an emulsifying agent (mannide monooleate), and heat-killed, dried Mycobacterium tuberculosis (or M. butyricum) cells. The mineral oil forms a depot at the injection site, slowing antigen release and prolonging immune stimulation. The Mycobacterium components — particularly muramyl dipeptide (MDP) from the bacterial cell wall — act as potent immunostimulants by activating macrophages and dendritic cells via Toll-like receptors (especially TLR2 and NOD2), triggering a strong Th1-polarised immune response characterised by IFN-γ and IL-12 production. FCA induces both humoral (antibody) and cell-mediated immunity and is widely used in animal experiments to raise high-titre antibodies. Freund's Incomplete Adjuvant (FIA) contains only mineral oil and emulsifier — it lacks Mycobacterium and produces a milder, predominantly humoral (Th2) response.

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