Immunology Review: Hypersensitivity and Autoimmunity

Hypersensitivity and Autoimmunity for the CLS Exam

Immunology is a critical subject for clinical laboratory scientists. This review covers the high-yield concepts tested on certification exams.

Type I Hypersensitivity (Immediate)

IgE-mediated. Allergen cross-links IgE on mast cells, causing degranulation (histamine release). Examples: anaphylaxis, allergic rhinitis, asthma.

Type II Hypersensitivity (Cytotoxic)

IgG/IgM against cell surface antigens. Examples: autoimmune hemolytic anemia (positive DAT), HDFN, Goodpasture syndrome, myasthenia gravis.

Type III Hypersensitivity (Immune Complex)

Antigen-antibody complexes deposit in tissues causing inflammation. Examples: SLE nephritis, serum sickness, post-streptococcal glomerulonephritis.

Type IV Hypersensitivity (Delayed)

T cell-mediated. No antibody involvement. Examples: PPD skin test, contact dermatitis, granulomatous diseases.

Key Autoantibodies

ANA (antinuclear antibody) for SLE screening. Anti-dsDNA is specific for SLE. RF (rheumatoid factor) for RA. Anti-CCP is more specific for RA. Anti-TPO for Hashimoto thyroiditis.