Diagram of patient JAK3 mutations. The coding region of wild-type JAK3 with its 7 JH domains is shown along with JAK3 mutations identified in the 6 SCID patients described in this report. For each patient, the cDNA mutation and resultant protein abnormality (in parentheses) are indicated. Note that patients 1, 2, and 4 are compound heterozygotes bearing 2 different mutations, whereas patients 3, 6, and 7 are homozygous for a single mutation. No mutations have been detected yet in patient 5. Nucleotide numbers correspond to the published cDNA sequence (U09607).²³  X indicates stop codon; and fs, frameshift.