Background:The clinical course and outcome of natural feline immunodeficiency virus (FIV) infection are variable and incompletely understood. Assigning clinical relevance to FIV infection in individual cats represents a considerable clinical challenge.Objective: To compare signalment, hematologic and biochemical data, major clinical problem, and survival among client-owned, FIV-infected, and uninfected domestic cats.Animals: Client-owned, domestic cats tested for FIV (n = 520). Methods: Retrospective, case control study. Logistic regression analyses were conducted to identify risk factors for FIV infection and to compare hematologic and biochemical data between cases and controls, after adjusting for potential confounders. Survival times were compared using Kaplan-Meier curves.Results: The prevalence of FIV infection was 14.6%. Mixed breed, male sex, and older age were risk factors for FIV infection. Hematologic abnormalities, biochemical abnormalities or both were common in both FIV-infected and uninfected cats. Lymphoid malignancies were slightly more common in FIV-infected than uninfected cats. Survival of FIVinfected cats was not significantly different from that of uninfected cats.Conclusions and Clinical Importance: Multiple hematologic and biochemical abnormalities are common in old, sick cats regardless of their FIV status. Their presence should not be assumed to indicate clinical progression of FIV infection. A negative effect of FIV on survival was not apparent in this study.

The IL2RG gene encoding the y chain of the lymphocyte receptor for IL-2 lies in human Xql3.1 and is mutated in males with X-linked severe combined immunodeficiency (SCID). In a large Canadian pedigree genetic linkage studies demonstrated that the proband's grandmother was the source of an X-linked SCID mutation. However, her T cells did not show the expected skewed X chromosome inactivation pattern of female'carriers of SCID, despite her having one affected son and two carrier daughters with skewed X inactivation. Single strand conformation polymorphism analysis of IL2RG in the affected proband was abnormal in exon 5; sequencing revealed a nine nucleotide in-frame duplication insertion. The three duplicated amino acids included the first tryptophan of the "WSXWS" motif found in all members of the cytokine receptor gene superfamily. Mutation detection in the pedigree confirmed that the founder' grandmother's somatic cells had only normal IL2RG, and further showed that the SC1D-associated X chromosome haplotype was inherited by three daughters, one with a wild type IL2RG gene and two others with the insertional mutation. Female germ line mosaicism is unusual, but its presence in this X-linked SCID family emphasizes the limitations of genetic diagnosis by linkage as compared with direct mutation analysis. (J. Cln. Invest 1995. 95:895-899.)

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IL2RG, the gene encoding the common gamma chain, gamma c, of the receptor for interleukin-2 and other cytokines, has been identified as the disease gene for severe combined immunodeficiency (SCID) of the X-linked type. Specific mutational diagnosis for X-linked SCID has thus become possible. For many women at risk for carrying an IL2RG mutation, no samples were saved from an affected male relative prior to either death or bone marrow transplantation (BMT). To establish optimal methods for genetic evaluation of such women, we compared mutational screening by single-strand conformational polymorphism, heteroduplex analysis and dideoxy fingerprinting (ddF). Abnormally migrating band patterns were followed up with direct sequencing for identification of specific mutations. The most sensitive method, ddF, detected heterozygous alterations, subsequently confirmed to represent significant mutations, in all of 19 unrelated obligate or suspected carriers studied. Some of these women, as well as others at risk for carrying an X-linked SCID mutation, enrolled in a study of prenatal diagnosis after fetal testing for gender determination. Originally using linkage analysis and, more recently, specific detection of IL2RG mutations, we evaluated pregnancies at risk for X-linked SCID prospectively on a research basis. Of 27 male fetuses tested 14 were predicted to be unaffected and confirmed to have normal immune status at birth. Among pregnancies predicted to be affected, 2 were terminated, while 11 affected males were born at term. Nine of these received neonatal BMT, one had BMT at 3 months of age, and one underwent a successful experimental in utero BMT. In our study cohort accurate prenatal diagnosis assisted decision making and expanded treatment options for families at risk for having infants with a severe, but treatable genetic disorder that presents early in life.