Write a short note on Passive Immunisation.

Definition

Passive immunisation is the administration of preformed antibodies, giving immediate but temporary protection (no immunological memory).

Sources / Types

• Natural — transplacental maternal antibodies; antibodies in breast milk.
• Immunoglobulins — normal human Ig, and specific Ig (hepatitis B Ig, tetanus Ig, VZIG, rabies Ig).
• Antisera/antitoxins — anti-tetanus serum, anti-diphtheria serum, anti-snake venom.

Uses

• Post-exposure prophylaxis (tetanus-prone wounds, rabies, hepatitis B exposure, varicella in high-risk contacts).
• Treatment (diphtheria antitoxin, snake envenomation) and in immunodeficiency.

Active VS Passive (contrast)

Unlike active immunisation (which is slow but durable), passive immunisation gives immediate protection but lasts only weeks to months and confers no memory; the two are often combined (e.g. Tetanus immunoglobulin plus toxoid).

Examples of Specific Immunoglobulins

• HBIG — hepatitis B exposure/newborn of HBsAg+ mother; TIG — tetanus-prone wounds.
• VZIG — varicella exposure in high-risk contacts; rabies Ig — category III animal bites (with vaccine).

Key Points Recap

• Preformed antibodies → immediate, short-lived protection, no memory.
• Uses: post-exposure prophylaxis (TIG, HBIG, VZIG, rabies Ig), antitoxin/antivenom, immunodeficiency.

Programme Note

Passive and active immunisation are complementary — for a tetanus-prone wound in an unimmunised person, tetanus immunoglobulin gives immediate cover while tetanus toxoid builds lasting immunity.