Identification of 3 new patients with recessive partial IFN-γR2 deficiency and MSMD. (A) Electropherogram showing the TCT-TTT mutation in P1 and the GGG-AGG mutation in P2 and P3 (indicated in red). (B) Familial segregation of the S124F and G141R mutations. Family A is from Mexico. Families B and C are from Turkey. E?, not genotyped. Healthy individuals are shown in white. Solid black shapes indicate patients with MSMD. The probands are indicated by arrows. Each kindred is designated by a capital letter (A-C), each generation by a roman numeral (I-III), and each individual by an Arabic number. (C) Schematic diagram of the IFNGR2 gene with all previously described mutations and the S124F and G141R mutations described here (highlighted by a red circle). Coding exons are numbered with roman numerals and delimited by a vertical bar. Regions corresponding to the leader sequence (L, 1-22), extracellular domain (EC, 23-248), transmembrane domain (TM, 249-272), and intracellular domain (IC, 273-337) are indicated. Mutations marked in red cause AR complete IFN-γR2 deficiency with no detectable expression of IFN-γR2 at the cell surface. The mutations marked in blue cause AR complete IFN-γR2 deficiency with detectable surface expression of a nonfunctional IFN-γR2. With the antibody now available, EBV-B cells from patients carrying the 663del27 mutations²³  and 382-387dup²⁵  were shown to have impaired and normal surface expression of IFN-γR2, respectively. The mutation marked in green causes AD partial IFN-γR2 deficiency. The mutations marked in purple cause AR partial IFN-γR2 deficiency.