The management and breeding of a large colony constitutes a major component of the genetic analysis of murine models of human diseases, requiring substantial effort in time and money. This mouse core will be the major component of the Wakeland mouse colony (WMC), which breeds and maintains an SPF colony that currently consists of >2000 mice. We have four specific aims: Specific aim 1. To maintain our collection of congenic strains and provide production mice as needed by the program project. A total of 23 strains are currently bred and maintained within the WMC. The core will be responsible for maintaining breeding records and overseeing the production of mice for experiments as needed by program project personnel. Specific aim 2. Production and maintenance of crosses. Large scale testcrosses and gene introgressions that are required by program project personnel will be supported by this core. Specific aim 3. Clinical and histological evaluations by SLE phenotypes. Several of the strains within this collection are susceptible to spontaneous systemic autoimmunity. These strains are inspected daily and monitored for proteinuria on a weekly basis beginning at 5 months of age. In addition, all tissue processing and histopathology will be centralized in Core B and performed under the supervision of Dr. Zhou. Specific aim 4. Derivation and importation of SPF strains. The WMC is housed in SPF conditions in a barrier facility. Importation of new strains is carefully monitored and in many instances, strains must be derived SPF prior to their admission into the facility. The WMC will develop Caesarian -derivation procedures for conversion to SPF status and supply this as a service to program project personnel. We anticipate that usage of this core will be: 70% Project 1, 25% Project 2, and 5% Projects 3 & 4.