Antigens in immune complexes from patients with breast cancer

Summary Sera and effusion fluids of patients with breast cancer (BC) contain immune complexes (IC). Antigens present in these complexes were isolated as follows: a pool of effusions from patients with BC was fractionated with ammonium sulfate. The proteins precipitating at 40% saturation were further fractionated by filtration through a Sephadex G-200 column. The material recovered in the first peak (molecules larger than monomeric IgG) was brought to pH 3.0 to dissociate the IC, and the mixture was filtered through a column of Sephacryl S-300 at pH 3.0. Proteins smaller than monomeric IgG were collected, radioiodinated, and used as antigens (¹²⁵Ag) to search for corresponding antibodies in sera of patients with BC (BCS) and of healthy individuals (NHS). ¹²⁵Ag was reacted with the sera and the immune complexes obtained were precipitated with an antiserum to human Ig and analyzed by SDS-polyacrylamide gel electrophoresis followed by autoradiography. Both NHS and BCS contained antibodies against two antigens; one of these appeared as a strong band of 17KD, the other as a doublet of approximately 25KD. It is concluded that some of the proteins in the IC from patients with BC are auto-antigens. No BC-specific antigens were identified.     

Are cytotoxic T cells a common homeostatic mechanism in responses to viruses, homografts and tumours?

Cytotoxic T cells (Tc) have been shown to be important in the rejection of histoincompatible tissue grafts. They are also generated in mice during infection with viruses that are known to express viral coded antigens at the infected cell surface, although their presence is much easier to demonstrate with some viral infections than with others. Cell-mediated lysis only occurs if the Tc and virus-infected target cells share gene products coded for in the K or D region of the H-2 complex. In the case of both ectromelia and influenza virus infection of mice, transfer of specific Tc to histocompatible, infected mice has been shown to significantly lower the virus titre in target organs (spleen and lungs respectively). In experimental animals with some tumours, there is increasingly good evidence for the expression of tumour specific transplantation antigens (TSTA) in the membrane of the malignant cells, yet there is little evidence for the presence of specific Tc which might control the growth of the tumour. Possible reasons for the lack of generation or expression of Tc in these situations are discussed.     

Static species distribution models in dynamically changing systems: how good can predictions really be?

It is widely acknowledged that species respond to climate change by range shifts. Robust predictions of such changes in species’ distributions are pivotal for conservation planning and policy making, and are thus major challenges in ecological research. Statistical species distribution models (SDMs) have been widely applied in this context, though they remain subject to criticism as they implicitly assume equilibrium, and incorporate neither dispersal, demographic processes nor biotic interactions explicitly. In this study, the effects of transient dynamics and ecological properties and processes on the prediction accuracy of SDMs for climate change projections were tested. A spatially explicit multi‐species dynamic population model was built, incorporating species‐specific and interspecific ecological processes, environmental stochasticity and climate change. Species distributions were sampled in different scenarios, and SDMs were estimated by applying generalised linear models (GLMs) and boosted regression trees (BRTs). Resulting model performances were related to prevailing ecological processes and temporal dynamics. SDM performance varied for different range dynamics. Prediction accuracies decreased when abrupt range shifts occurred as species were outpaced by the rate of climate change, and increased again when a new equilibrium situation was realised. When ranges contracted, prediction accuracies increased as the absences were predicted well. Far‐dispersing species were faster in tracking climate change, and were predicted more accurately by SDMs than short‐dispersing species. BRTs mostly outperformed GLMs. The presence of a predator, and the inclusion of its incidence as an environmental predictor, made BRTs and GLMs perform similarly. Results are discussed in light of other studies dealing with effects of ecological traits and processes on SDM performance. Perspectives are given on further advancements of SDMs and for possible interfaces with more mechanistic approaches in order to improve predictions under environmental change.