Immune system formulas

Immune system: lymphoid organs, innate immunity, complement and antibodies. 4 formulas for GATE BT General Biology, each with when to use it. Each is explained in the topic notes.

All 4 Immune system formulas

C3 CONVERTASES

C3 convertase: C4b2a (classical, lectin), C3bBb (alternative)

Each cleaves C3 into C3a (anaphylatoxin) and C3b (opsonin); C3b joining the convertase makes the C5 convertase.

TERMINAL PATHWAY AND MEMBRANE ATTACK COMPLEX

C5 C5 convertase C5a + C5b; C5b + C6 + C7 + C8 + n C9 \to MAC

Common to all pathways. The MAC is a pore that lyses Gram-negative bacteria and other susceptible cells.

VALENCY OF AN ANTIBODY

binding sites = 2 \times (number of monomer units)

Applies when each monomer has two sites: IgG, IgE, IgD = 2; secretory IgA dimer = 4; IgM pentamer = 10.

COMBINATORIAL DIVERSITY

N_{H} = V_{H} \times D_{H} \times J_{H}, N_{L} = V_{κ} J_{κ} + V_{λ} J_{λ}

Counts of functional segments. Total combinations are N_H x N_L (assuming any heavy chain pairs with any light chain), before junctional diversity and somatic hypermutation are added.

Where this was asked: 2019 (1), 2020 (1), 2022 (1), 2024 (2), 2026 (1). See the 6 previous-year questions on Immune system. This shows what was asked, not what will be asked.

KEEP GOING

Immune system: the notes and 6 solved previous-year questions