ABD Basic Science and Immunology 3

Question 1

Melanin is synthesized from which amino acid precursor via the enzyme tyrosinase?

Accepted Answer

Tyrosine

Answer

Tyrosinase converts tyrosine to DOPA and then dopaquinone in melanogenesis.

Question 2

Which cell adhesion structure connects adjacent keratinocytes and is targeted by autoantibodies in pemphigus vulgaris?

Accepted Answer

Desmosome

Answer

Desmosomes (via desmoglein 3) are disrupted in pemphigus vulgaris causing acantholysis.

Question 3

Type VII collagen, defective in dystrophic epidermolysis bullosa, forms which structure?

Accepted Answer

Anchoring fibrils

Answer

Type VII collagen forms anchoring fibrils that attach the lamina densa to dermis.

Question 4

The complement pathway activated directly by antigen-antibody complexes begins with which component?

Accepted Answer

C1

Answer

The classical pathway is initiated by C1 binding to antibody-antigen complexes.

Question 5

Which vitamin is synthesized in the skin from 7-dehydrocholesterol upon UVB exposure?

Accepted Answer

Vitamin D

Answer

UVB converts 7-dehydrocholesterol to previtamin D3 in the epidermis.

American Board of Dermatology (ABD) Practice Test