16. DiGeorge’s syndrome is characterized by the lack of a thymus The mouse model closest to this human disease would be a

A. knock-out mouse for RAG-1 and RAG-2
B. knock-out mouse for a thymus
C. nude mouse
D. recombinant mouse for CD3

17. Which of the Rous sarcoma virus has a homologous cellular protein?

A. c-src
B. v-src
C. v-ha-src
D. v-ha-ras

18. Infants are most susceptible to bacterial infection due to low circulating levels of IgG

A. in utero (before birth)
B. at 0-3 months of age
C. at 3-12 months of age
D. at 12-24 months of age

19. The chemical, typically released by the body in an allergic response is

A. histamine
B. allergens
C. antihistamines
D. perforins