Identification of four new quantitative trait loci regulating arthritis severity and one new quantitative trait locus regulating autoantibody production in rats with collagen-induced arthritis.

OBJECTIVE: Collagen-induced arthritis (CIA) is a polygenic model of experimentally induced autoimmunity and chronic joint inflammation. This study maps genetic loci that regulate CIA susceptibility in DA/Bkl (DA) and BN/SsNHsd (BN) rats. METHODS: Genome scans covering chromosomes 1-20 and interval mapping techniques using 159 simple sequence-length polymorphism markers were used to identify quantitative trait loci (QTLs) that regulate CIA in (DA x BN)F2 hybrids. Serum antibody titers to type II collagen were determined by enzyme-linked immunosorbent assay. RESULTS: DA rats were high responders to porcine type II collagen (PII) and developed severe CIA (100%). BN rats were low responders to PII and resistant to CIA (0%). BN genes strongly repressed PII-induced CIA. Only 12% of (DA x BN)F1 rats (7 of 60) and 31% of (DA x BN)F2 rats (307 of 1,004) developed CIA. Three new QTLs (Cia11, Cia12, and Cia13) with significant logarithm of odds (LOD) scores of 5.6, 4.6, and 4.5, respectively, plus a suggestive QTL (Cia14*, LOD 3.0) regulating arthritis severity were identified on chromosomes 3, 12, 4, and 19. A new QTL, Ciaa3, associating with anticollagen antibody titer (antibody to PII LOD 6.5; antibody to rat type II collagen LOD 5.2) mapped to chromosome 9. Of 10 CIA QTLs previously identified in (DA x F344) and (DA x ACI) rats, only Cia1 in the major histocompatibility complex and a region coincident to Cia5 on chromosome 10 (LOD >8.0) influenced CIA severity in (DA x BN)F2 rats. CONCLUSION: Since CIA exhibits many of the pathologic features of rheumatoid arthritis, the data indicate that the variety of genetic elements regulating human autoimmune and rheumatic diseases may be much larger and more varied than originally envisioned.

Identification of a new non-major histocompatibility complex genetic locus on chromosome 2 that controls disease severity in collagen-induced arthritis in rats.

OBJECTIVE: To identify novel non-major histocompatibility complex (non-MHC) genetic loci controlling the severity of homologous rat type II collagen-induced arthritis (CIA). METHODS: We conducted a genome-wide scan to identify CIA regulatory quantitative trait loci (QTL) in an F2 cross between DA (CIA highly susceptible) and ACI (CIA resistant) inbred rats immunized with homologous rat type II collagen (RII). These strains share the MHC/RT1av1 haplotype required for susceptibility to RII-induced CIA. RESULTS: F2 females had higher median arthritis scores than did males. Relative resistance in the males was determined by inheriting either a DA or an ACI Y chromosome and was independent of the source of the X chromosome. In addition, a major QTL was localized on chromosome 2 (Cia7, logarithm of odds score 4.6). Cia7 is in a region that shows linkage conservation with chromosomal regions that regulate autoimmune diabetes and experimental autoimmune encephalomyelitis in mice and multiple sclerosis in humans. CONCLUSION: Sex chromosomes and Cia7 play an important role in regulating CIA in response to RII. This rat model should facilitate positional cloning and functional characterization of regulatory genes that may play a role in several forms of autoimmune disease, including rheumatoid arthritis.

A survey of fluoroscopic exposure rates: AAPM Task Group No. 11 Report.

Fluoroscopic procedures, in general, result in much higher exposures to patients than do most types of radiographic procedures [National Council on Radiation Protection, Report 100, p. 31 (1989)]. In spite of this, fluoroscopic exposure rates can vary widely between systems, and often for no apparent reason. The charge of AAPM Task Group No. 11 was to evaluate fluoroscopic exposure rates at the entrant surface of the x-ray image intensifier, and to disseminate this information so that medical physicists could compare their own exposure rate measurements with typical values. The measurement protocol was defined for various system configurations. Sheets of copper were used to attenuate the x-ray beam, and the input exposure rate at the image intensifier (at the input mode closest to 23-cm diameter) in the absence of a scattering medium was determined. With 2 mm of copper as x-ray beam filtration, the median fluoroscopic exposure rate at the image intensifier was found to be 16.5 nC/kg/s (64.0 microR/s), with an average kV of 77 and mA of 2.0 (n = 62).

Karyotypic evolution associated with loss of tumorigenicity.

A reproducible association between loss of tumorigenicity and specific karyotypic changes was described in cell culture lines SLU-5 and DMS-402 established from mouse plasmacytoma MOPC-21 carried in BALB/c mice. The defect in chromosome no. 15, which has been specifically associated with mouse myelomas, was neither corrected nor eliminated in the karyotypic evolution that occurred simultaneously and progressively with the grandual loss of oncogenicity.

A specific chromosome breakpoint associated with mouse plasmacytomas.

The chromosomes of uncultured cells of the near-diploid mouse plasmacytoma MOPC-31C were studied. The modal number of chromosomes was 44. The tumor lacked two marker chromosomes, reciprocal translocation [rcp t(12; 15)], that in previous studies were found to be common to 3 other uncultured myelomas and 1 cultured mouse myeloma. Through the formation of two markers, rcp t(6; 15), unique to this tumor, however, the tumor shared with other tumors and their specific markers a common breakpoint in chromosome "15 at band D3/E. This breakpoint has been found in all mouse plasmacytomas examined with banding thus far and is considered of possible importance in the development of this tumor.

Karyotype, marker formation, and oncogenicity in mouse plasmacytomas.

Two common chromosome markers in the 2 plasmacytomas previously examined by Giemsa banding were consistently present in the mouse plasmacytoma X-5563, a transplantable hypertetraploid tumor of spontaneous origin in C3H mice. The 2 markers were found in both induced and spontaneous tumors and in either BALB/c or C3H mice. The derived cell line had 17 fewer chromosomes than the X-5563 tumor and was oncogenic, and its modal karyotype was identical to that of the tumor transmitted by the inoculation of the cell line. The homogeneity of a slight karyotypic modification in a second tumor suggested a possible clonal origin of that tumor. The high frequency of centric fusions between homologues and the structure of certain markers suggests that homologue association may precede marker formation. We proposed a second mechanism of marker formation, selective regional elongation, to account for the larger number of markers with proximal or distal elongations without evidence of translocation and for the observed alterations in length and banding pattern of markers after growth in vitro. Comparison of MOPC-21, MOPC-315, and X-5563 tumors showed preferential involvement of certain chromosomes in marker formation, an inferred association of the 2 common markers with an early stage in the origin of the 3 plasmacytomas, and consistent loss of an X chromosome. Loss of oncogenicity in cell lines was associated with a number of karyotypic changes, but did not require the loss of the characteristic markers or additional copies of a specific normal chromosome.