Infected reindeer did not have clinical signs of TB or disseminated disease after 1 year of colonization, suggesting low-grade chronic infection. Strains of or other spp. within the complex, however, have not been isolated from these reindeer upon necropsy. Reasons for the high rate of false-positive reactions elicited by skin testing are unclear, although it may be due to unusual exposure to nontuberculous spp. or an exaggerated cellular immune response to mycobacterial antigens. Therefore, improved TB tests are urgently needed to avoid the unnecessary slaughter of reindeer falsely identified as TB reactors. For TB surveillance of captive wildlife (e.g., zoos or game farms) and nontraditional livestock, blood-based TB assays are appealing, as they require a single handling event, thereby minimizing capture-associated injuries. Blood-based assays are also more readily used in capture surveillance programs with free-ranging wildlife (e.g., white-tailed deer [infection studies are necessary to characterize the humoral immune response and to identify the most reactive antigens that E3 ligase Ligand 9 could be employed in serodiagnostic tests. Previous studies with cattle and white-tailed deer have revealed both similarities and differences in the antibody responses against infection of these two species (17, 18, 34). In particular, E3 ligase Ligand 9 antigen recognition patterns appear to differ from animal to animal in both species, and antibody levels are significantly elevated shortly after the intradermal tuberculin injection(s) for skin testing. Little, if anything, is known concerning antibody responses of reindeer to infection. The present study describes the humoral response of reindeer to experimental infection with infection, the challenge inoculum (105 CFU in 0.2 ml of phosphate buffered saline [PBS], pH 7.2) was instilled directly into the tonsillar crypts of anesthetized reindeer (= 11) as described for the inoculation of white-tailed deer (21). The strain of used for the challenge inoculum (95-1315 [USDA, Animal Plant and Health Inspection Service APHIS designation]) was originally isolated from a E3 ligase Ligand 9 white-tailed deer in Michigan (24). Inoculum consisted of mid-log-phase cells grown in Middlebrook’s 7H9 medium supplemented with 10% oleic acid-albumin-dextrose complex (Difco, Detroit, Michigan) plus 0.05% Tween 80 (Sigma Chemical Co., St. Louis, Missouri). At the time of inoculation, reindeer were moved from an outdoor pen into climate-controlled rooms (two to three animals/room) within a biosafety level 3 confinement facility. Negative airflow exited the building through HEPA filters, ensuring that air from animal pens was pulled towards a central corridor and through HEPA filters before exiting the building. The airflow velocity was 10.4 air changes/h. Four noninoculated reindeer were housed in a climate-controlled room in a building (biosafety level 2 facility) separate from the building in which the infected reindeer were housed. Additionally, serum samples from 19 reindeer housed outdoors at the National Animal Disease Center were obtained. Thirteen months after inoculation, reindeer in the infected (= 11) and noninoculated (= 4) groups were euthanized by an intravenous injection of sodium MYCNOT pentobarbital (Fort E3 ligase Ligand 9 Dodge Animal Health, Fort Dodge, Iowa) and examined. Various tissues were collected for bacteriologic culture and microscopic examination. Detailed descriptions of cellular immune responses (35), bacteriologic culture, histopathology, and gross necropsy results are presented elsewhere (23). CCT. Ninety days after inoculation, reindeer were tested for in vivo responsiveness to mycobacterial antigens by a modified CCT technique enabling the collection of biopsy specimens for E3 ligase Ligand 9 which the dermal reactions to purified protein derivatives (PPDs) at 24, 48, and 72 h postinjection could be analyzed (23, 33). Briefly, the cervical region was clipped and animals injected intradermally in three separate locations with PPD and a single location with PPD (PPDs obtained from National Veterinary Services Laboratory, Ames, Iowa). A standard CCT (i.e., single intradermal injection each of PPD and PPD) was performed 8 months after inoculation (22, 29). For each of the skin tests, 100 g of PPD and 40 g of PPD were administered at each respective location according to guidelines described in USDA, APHIS circular 91-45-011 (29). Skin thickness at each injection site was measured prior to injection of PPDs and 72 h after administration. Changes in skin thickness were calculated and responses plotted on a scattergram developed by USDA for the interpretation of the CCT for bison, cattle, and cervidae (Form VS-6-22D). Responses by individual reindeer within both infected and noninfected groups are presented elsewhere (23). Enzyme-linked immunosorbent assay (ELISA). Lipoarabinomannan (LAM)-enriched mycobacterial antigen was prepared from strain 95-1315 as described previously (31). Briefly, bacilli harvested from 4-week cultures were sonicated in PBS, further disrupted with 0.1- to 0.15-mm glass beads (Biospec Products, Bartlesville, Oklahoma) in a bead beater (Biospec Products), centrifuged, filtered (0.22-m-pore-size filter), and digested in a 1-mg/ml proteinase K (Roche Molecular Biochemicals, Indianapolis, Indiana) solution (50 mM Tris, 1.