To characterize thymic epithelial cells of SCID (severe combined immunodeficiency) mice in comparison with those of Balb C mice, we did an immunohistochemical study using cortical and medullary epithelial cell specific monoclonal antibodies (MoAbs), Th-3 and Th-4, as well as gel electrophoresis and immunoblotting. The thymi of SCID mice were composed of epithelial cells and a few lymphocytes. Most epithelial cells were immunostained diffusely with Th-3, which indicated that they might be "cortical-type" epithelial cells. There were a few clusters of stellate cells with dendritic processes which were negative with Th-3 but stained strongly with Th-4. Cortical type epithelial cells and most of the Th-4 reacting cells were strongly immunostained with cytokeratin antibody MNF116. By immunoblotting, cytokeratin polypeptides No. 10 and 18 were detected in both SCID and Balb C mice; however, the relative amounts of each cytokeratin polypeptides were different. With immunohistochemical and immunoblotting results, we conclude; 1) Th-3 and Th-4 are reliable markers for cortical and medullary thymic epithelial cells in SCID mice; 2) disorganization of cells thymic structure is mostly due to maldevelopment of medullary epithelial and T lymphocytes; and 3) the composition of cytokeratin subfamilies of SCID mice thymi may represent a phenotypic marker of the maldevelopment of medullary epithelial cells.
Animals ; Antibodies, Monoclonal ; Electrophoresis, Polyacrylamide Gel ; Epithelium/pathology ; Immunoblotting ; Keratins/analysis ; Mice ; Mice, Inbred BALB C ; Mice, SCID ; Severe Combined Immunodeficiency/*pathology ; Thymus Gland/*pathology

OBJECTIVEOmenn syndrome is a rare autosomal recessive hereditary severe combined immunodeficiency. The purpose of this study was to understand clinical characteristics and genetic mutation type of Omenn syndrome and to improve the recognition of Omenn syndrome among pediatric clinicians.

METHODOne suspected case of severe combined immunodeficiency was found to have pneumonia repeatedly, intractable diarrhea, poor antibiotic treatment effect, lymphadenopathy, hepatosplenomegaly and erythroderma. The patient was diagnosed as having Omenn syndrome by RT-PCR, and the expression of RAG1/RAG2 and gene analysis of RAG1/RAG2 were performed.

RESULTThe classification of lymphocyte was CD3(+) cells (35.3%), CD19(+) cells (0.4%), CD16(+) cells (57.6%). After stimulation with phytohemagglutinin (PHA), lymphocyte proliferation of the child was extremely low. Genetic studies showed RAG1 homozygous deletion mutation (2302 del T). He had detectable activated T-lymphocytes with low circulating B-lymphocytes and no evidence of maternal T-cell engrafment as indicated by the short tandem repeat (STR) analysis.

CONCLUSIONOmenn syndrome is a severe combined immunodeficiency disease caused by mutations in the RAG1/RAG2 gene. The disease has been reported rarely in China. The clinical manifestations of the disease is early postnatal repeated infections and erythroderma. Mutation analysis of RAG1/RAG2 gene may help to confirm the diagnosis and may be useful in early immune reconstitution and genetic counseling.

Amino Acid Sequence ; Biomarkers ; blood ; DNA Mutational Analysis ; DNA-Binding Proteins ; genetics ; Genotype ; Homeodomain Proteins ; genetics ; Humans ; Infant ; Lymphocytes ; immunology ; pathology ; Male ; Microsatellite Repeats ; Mutation ; Nuclear Proteins ; genetics ; Phenotype ; Receptors, Antigen, T-Cell, alpha-beta ; genetics ; Reverse Transcriptase Polymerase Chain Reaction ; Severe Combined Immunodeficiency ; diagnosis ; genetics ; pathology