Antibodies are host proteins that comprise one of the principal effectors of the adaptive immune system. Their utility has been harnessed as they have been and continue to be used extensively as a diagnostic and research reagent. They are also becoming an important therapeutic tool in the clinician's armamentarium to treat disease. Antibodies are utilized for analysis, purification, and enrichment, and to mediate or modulate physiological responses. This overview of the structure and function of polyclonal and monoclonal antibodies describes features that distinguish one from the other. A limited review of their use as specific research, diagnostic, and therapeutic reagents and a list of printed and electronic resources that can be utilized to garner additional information on these topics are also included.

Monoclonal antibody (MAb) production via the growth of ascitic tumors in mice has been the time-honored technique for producing small scale, research laboratory quantities of MAbs. There are many disadvantages associated with MAb production in murine ascites, including animal welfare concerns. Small scale, commercially available, hollow fiber bioreactor systems, which appear to have advantages over other in vitro cell culture techniques, have recently been introduced. To the author's knowledge, these bioreactor systems have not been independently evaluated as a potential alternative to the in vivo production of MAbs in murine ascites. The first objective of this study was to characterize the clinicopathologic changes in mice associated with the in vivo production of MAbs. Five different hybridoma cell lines were grown in groups of 20 mice. Mice were primed with 0.5 ml pristane intraperitoneally 14 days prior to inoculation of 1 x 106 hybridoma cells.Abdominal paracentesis was performed a maximum of 3 times for collection of ascites from each mouse; ascites volumes were recorded. Clinical observations, body weight measurements, and postmortem examinations were performed. Incidence and severity of clinical abnormalities increased with time. Disseminated intraabdominal seeding of tumor and/or solid tumor masses were observed at postmortem examination. The second objective of the study was to compare MAb production in mice versus hollow fiber bioreactor systems to determine the feasibility of these systems as potential alternatives to the use of mice. Three hybridoma cell lines were grown in each of three different commercially available hollow fiber bioreactor systems and in groups of 20 mice. Bioreactors were harvested 3 times weekly for 65 days and were monitored by cell counts, cell viability and media glucose consumption. Time and materials logs were maintained. Time spent in labor and materials costs were greater for the bioreactors than the mice. The mean antibody concentration, as determined by ELISAs, in mouse ascites versus the range of mean concentrations for the 3 bioreactor systems for each cell line were as follows: cell line 2B11, 4.22 mg/ml vs. 0.71 to 1.31 mg/ml; cell line 3C9, 4.07 mg/ml vs. 1023.06 mg. Significant clinicopathologic changes in mice were associated with MAb production in ascites. Although time and materials costs were greater for the bioreactors, these results suggest that hollow fiber bioreactor systems merit further investigation as potentially viable alternatives to the use of mice for MAb production.2 ACKNOWLEDGEMENTS

Chlamydia muridarum (Cm) was detected in 2 colonies of mice with lymphoplasmacytic pulmonary infiltrates by using PCR and immunohistochemistry. This discovery was unexpected, as Cm infection had not been reported in laboratory mice since the 1940s. A Cm specific PCR assay was developed and testing implemented for the resident colonies of 8 vivaria from 3 academic institutions, 58 incoming mouse shipments from 39 academic institutions, and mice received from 55 commercial breeding colonies (4 vendors). To estimate Cm’s global prevalence in research colonies, a database containing 11,387 metagenomic fecal microbiota samples from 120 institutions and a cohort of 900 diagnostic samples from 96 institutions were examined. Results indicate significant prevalence among academic institutions, with Cm detected in 63% of soiled bedding sentinels from 3 institutions; 33% of incoming mouse shipments from 39 academic institutions; 14% of 120 institutions submitting microbiota samples; and 16% of the diagnostic sample cohort. All samples from commercial breeding colonies were negative. In addition, naïve NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice exposed to Cm-shedding mice and/or their soiled bedding developed clinical disease at 21 to 28 d after exposure. These mice had a moderate-to-severe histiocytic and neutrophilic bronchointerstitial pneumonia, with their respiratory epithelium demonstrating inclusions, chlamydial major outer membrane protein immunostaining, and hybridization with a Cm reference sequence (GenBank accession no. U68436). Cm was isolated from lungs, cecum, and feces of a Cm-infected NSG mouse by using HeLa 229 cells. The considerable prevalence of Cm is likely due to widespread global interinstitutional distribution of unique mouse strains and failure to recognize that some of these mice were from enzootically infected colonies. Given that experimental Cm colonization of mice results in a robust immune response and, on occasion, pathology, natural infection may confound experimental results. Therefore, Cm should be excluded and eradicated from enzootically infected mouse colonies.