Outgrowth In Mice Research Articles

Aspiration pneumonitis primes the host for an exaggerated inflammatory response during pneumonia*

Nosocomial pneumonia is a feared complication in the critically ill patient. Aspiration pneumonitis is frequently complicated by infections. The objective of this study was to determine the influence of aspiration pneumonitis on the host response to a common nosocomial respiratory pathogen. Controlled, in vivo laboratory study. Research laboratory of a health sciences university. Female C57Bl/6 mice. Mice received hydrochloric acid or saline intratracheally followed 16 hrs later by Klebsiella pneumoniae. Hydrochloric acid induced a mild aspiration pneumonitis. Nonetheless, hydrochloric acid aspiration resulted in a markedly increased inflammatory response in the lung on infection with K. pneumoniae. This enhanced inflammatory reaction was accompanied by a greatly increased outgrowth of K. pneumoniae in lungs of mice previously exposed to hydrochloric acid. Preexisting aspiration pneumonitis also triggered mouse lungs in vivo and alveolar macrophages ex vivo for enhanced release of proinflammatory mediators on stimulation with Klebsiella lipopolysaccharide. Inhibition of tumor necrosis factor-alpha resulted in an increased inflammatory reaction and enhanced bacterial outgrowth in mice with primary K. pneumoniae pneumonia, whereas it had no effect in mice with preexisting aspiration pneumonitis. These data indicate a) that aspiration pneumonitis renders the host more susceptible to respiratory tract infection with K. pneumoniae, concurrently priming the lung for an exaggerated inflammatory response; and b) that although tumor necrosis factor-alpha plays a major role in the host response to primary infection, it does not affect lung inflammation or defense after aspiration pneumonitis.

Enhanced tumour growth after DNA vaccination against human papilloma virus E7 oncoprotein: evidence for tumour-induced immune deviation

We have examined the induction of anti-tumour immunity in a murine model using a gene vaccine approach to deliver a well defined tumour antigen. The vaccines expressed the human papilloma virus type 16 (HPV 16) E7 oncoprotein, and protection was measured against HPV 16-expressing C3R tumour cell line in vivo. In control mice injected with saline, C3R cells initially formed tumours but then regressed completely. As expected, animals injected with a peptide that represents the D b-presented CTL epitope from E7 (RAHYNIVTF) were completely protected from tumour growth. Contrary to expectation, however, we consistently saw enhanced tumour growth, delayed regression, or tumour outgrowth in mice vaccinated with two different E7-expressing DNA vaccines. We found no evidence for loss of D b or K b class I MHC molecules from C3R cells recovered from outgrown tumours, and fluorescent MHC/peptide tetramer staining revealed E7 gene vaccination did not delete RAHYNIVTF-specific CD8 + T cells. However, we did observe an effect on cytokine production. Splenocytes from E7 gene vaccinated animals responded to re-stimulation in vitro with C3R cells by producing IL-4 but background levels of IFN-γ. We also observed that cytokine production and E7 peptide-specific CTL were only detectable in vaccinated animals after C3R challenge, but not after DNA priming alone. We conclude that ‘prime-boosting’ is necessary to observe tumour-specific T cell responses with the gene vaccine approach, but that boosting with tumour cells causes skewing of the primed cells in a T2 direction that is incompatible with protective anti-tumour immunity.

The effects of UV waveband and cis-urocanic acid on tumour outgrowth in mice.

Immunogenic murine tumours that are normally rejected upon transplantation into syngeneic hosts grow progressively if the hosts are UV-irradiated prior to tumour implantation. Using three sources of UV we investigated the most effective waveband and dose for increased outgrowth of injected fibrosarcoma (FSA) cells in mice, compared with unirradiated controls. The animals were exposed on their shaved dorsal skin twice a week for 3 weeks to either broad-band (TL12) or narrow-band (TL01) UVB, or UVA-I radiation; FSA cells were then injected subcutaneously into the UV-irradiated skin. Exposure to TL12 at doses higher than 1000 J m(-2), but not TL01 or UVA-I, caused increased outgrowth of the injected tumour cells. The effect of the UV irradiation seemed to be local as injection of the FSA cells into the unirradiated ventral skin of mice irradiated with TL12 on the dorsal surface did not result in increased outgrowth of the tumours. Cis-urocanic acid, a recognised initiator of UV-induced immunosuppression, applied topically or intradermally for 3 weeks prior to FSA cell injection, had no effect on the rate of tumour outgrowth. Similarly, injection of a monoclonal antibody with specificity for cis-urocanic acid, prior to each irradiation with TL12, did not reverse the increased growth of FSA cells injected into the UV-irradiated skin. Thus wavelengths within the broad-band UVB range are the most effective for inducing increased outgrowth of FSA cells; cis-urocanic acid is not an important mediator in this UV-enhanced growth of tumours.

Mammary epithelial stem cells.

It has recently been shown that the progeny from a single cell may comprise the epithelial population of a fully developed lactating mammary outgrowth in mice. Serial transplantation of epithelial fragments from this clonally derived gland demonstrates that the subsequently generated outgrowths are also comprised of progeny from the original antecedent. All epithelial cell types were found to be present within these clonal normal populations including luminal, myoepithelial, ductal, and lobule-committed epithelial progenitors and fully competent mammary epithelial stem cells. These observations demonstrate the presence of multipotent tissue-specific epithelial stem cells among the parenchyma of the murine mammary gland. Similarly, genetic analysis of contiguous portions of individual human mammary ducts within the same breast indicates their clonal derivation. Here, we discuss the properties, location, division-potential, senescence, and plasticity associated with mammary epithelial stem cells and present the developing evidence for their presence in human breast and their important role in the risk for breast cancer development. Further, we review the present morphologic and genetic evidence for the characterization of specific stem cell markers and lineage-limited progenitor cells in human and rodent mammary epithelium. Microsc. Res. Tech. 52:190-203, 2001. Published 2001 Wiley-Liss, Inc.

Mammary epithelial stem cells: our current understanding.

It has recently been shown that the progeny from a single cell may comprise the epithelial population of a fully developed lactating mammary outgrowth in mice. Serial transplantation of epithelial fragments from this clonally derived gland demonstrates that the subsequently generated outgrowths are also comprised of progeny from the original antecedent. Similarly, genetic analysis of contiguous portions of individual human mammary ducts within the same breast indicates their clonal derivation. These observations support the concept that multipotent tissue-specific epithelial stem cells are present among the parenchymal cells of the mammary gland. Here, we present the developing evidence for the presence of stem cells in virtually every renewing mammalian tissue as well as some classically considered to consist only of differentiated cells. Further, we review the present morphologic and biologic evidence for stem cells and lineage-limited progenitor cells in human and rodent mammary epithelium. Although a number of selective markers are known for various lineage-limited hematopoietic cells and their progeny, our understanding of the biology of the precursor cells for mammary epithelium is just beginning. Our purpose here is to develop further interest in the clarification of these issues in the biology of the mammary gland.