ABSTRACT
Tamoxifen (TAM) inducible Cre recombinase system is an essential tool to study gene function when early ablation or overexpression can cause developmental defects or embryonic lethality. However, there remains a lack of consensus on the optimal route and dosage of TAM administration in vivo. Here, we assessed dosage and delivery of TAM for activation of Cre in immune cell subsets assessed longitudinally and spatially using transgenic mice with ubiquitously expressed Cre/ER and the Cre-inducible fluorescent reporter YFP. After comparing two TAM delivery methods (intraperitoneal versus oral gavage) and different doses, we found that 3 mg of TAM administered orally for five consecutive days provides maximal reporter induction with minimal adverse effects in vivo. Serum levels of TAM peaked 1 week after initiating treatment then slowly decreased, regardless of dosing and delivery methods. TAM concentration in specific tissues (liver, spleen, lymph nodes, and thymus) was also dependent on delivery method and dose. Cre induction was highest in myeloid cells and B cells and substantially lower in T cells, and double-positive thymocytes had a notably higher response to TAM. In addition to establishing optimal dose and administration of TAM, our study reveals a disparate activity of Cre in different cell immune populations when using Cre/ER models.
Subject(s)
Immune System/cytology , Immune System/enzymology , Integrases/biosynthesis , Tamoxifen/pharmacology , Administration, Oral , Animals , Bacterial Proteins/biosynthesis , Bacterial Proteins/genetics , Dose-Response Relationship, Drug , Enzyme Induction/drug effects , Female , Genes, Reporter , Immune System/drug effects , Injections, Intraperitoneal , Integrases/genetics , Leukocyte Common Antigens/metabolism , Liver/cytology , Liver/drug effects , Liver/immunology , Luminescent Proteins/biosynthesis , Luminescent Proteins/genetics , Lymphoid Tissue/cytology , Lymphoid Tissue/drug effects , Lymphoid Tissue/immunology , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Spleen/cytology , Spleen/drug effects , Spleen/immunology , Tamoxifen/administration & dosage , Tamoxifen/pharmacokineticsABSTRACT
Rabbit-origin enteropathogenic Escherichia coli (EPEC) causes substantial diarrhea-associated morbidity and has zoonotic potential. A culture-based survey was undertaken to ascertain its prevalence. EPEC was isolated from 6/141 (4.3%) commercially-acquired laboratory rabbits. Three of these did not have diarrhea or EPEC-typical intestinal lesions; they instead had background plasmacytic intestinal inflammation. Asymptomatically infected rabbits may function as EPEC reservoirs.
