Immunopathology mnemonic

The four types of hypersensitivity

The mnemonic

ACID

What each word stands for

  • AType I: Anaphylactic (IgE)
  • CType II: Cytotoxic (antibody to cell surface)
  • IType III: Immune complex
  • DType IV: Delayed (T-cell mediated)

Why it matters clinically

Examples: anaphylaxis (I), haemolytic transfusion reaction (II), serum sickness (III), contact dermatitis and tuberculin reaction (IV).

Where it stops being reliable

Some conditions straddle categories, and type V (stimulating or blocking antibodies, as in Graves disease) is sometimes added.

Teaching aid, still awaiting independent review. Confirm facts in a standard source.

More mnemonics

Common questions

What is the Immunopathology mnemonic?

ACID. It helps you recall: The four types of hypersensitivity.

What does "A" stand for?

Type I: Anaphylactic (IgE)

What does "C" stand for?

Type II: Cytotoxic (antibody to cell surface)

What does "I" stand for?

Type III: Immune complex

What are all the parts of the ACID mnemonic?

A: Type I: Anaphylactic (IgE); C: Type II: Cytotoxic (antibody to cell surface); I: Type III: Immune complex; D: Type IV: Delayed (T-cell mediated).

Which topic does this mnemonic belong to?

It belongs to Immunopathology in Pathology.

Where does this mnemonic stop being reliable?

Some conditions straddle categories, and type V (stimulating or blocking antibodies, as in Graves disease) is sometimes added.

How is this useful clinically?

Examples: anaphylaxis (I), haemolytic transfusion reaction (II), serum sickness (III), contact dermatitis and tuberculin reaction (IV).

How do I make this mnemonic stick?

Say it aloud, write it from memory tomorrow, then again in a week. Then test yourself on a Pathology question about Immunopathology.

Is this a standard mnemonic?

It is a teaching aid written or adapted by our team. Some resemble ones students share informally. Check any fact that matters in a standard source.