Semiconductor nanocrystals were prepared for use as fluorescent probes in biological staining and diagnostics. Compared with conventional fluorophores, the nanocrystals have a narrow, tunable, symmetric emission spectrum and are photochemically stable. The advantages of the broad, continuous excitation spectrum were demonstrated in a dual-emission, single-excitation labeling experiment on mouse fibroblasts. These nanocrystal probes are thus complementary and in some cases may be superior to existing fluorophores.

https://science.sciencemag.org/content/sci/281/5385/2013.full.pdf

Semiconductor Nanocrystals as Fluorescent Biological Labels

Evolution by gene duplication

The classical pathway of interferon-gamma-dependent activation of macrophages by T helper 1 (T(H)1)-type responses is a well-established feature of cellular immunity to infection with intracellular pathogens, such as Mycobacterium tuberculosis and HIV. The concept of an alternative pathway of macrophage activation by the T(H)2-type cytokines interleukin-4 (IL-4) and IL-13 has gained credence in the past decade, to account for a distinctive macrophage phenotype that is consistent with a different role in humoral immunity and repair. In this review, I assess the evidence in favour of alternative macrophage activation in the light of macrophage heterogeneity, and define its limits and relevance to a range of immune and inflammatory conditions.

Alternative activation of macrophages

Approximately 10% of peripheral CD4+ cells and less than 1% of CD8+ cells in normal unimmunized adult mice express the IL-2 receptor alpha-chain (CD25) molecules. When CD4+ cell suspensions prepared from BALB/c nu/+ mice lymph nodes and spleens were depleted of CD25+ cells by specific mAb and C, and then inoculated into BALB/c athymic nude (nu/nu) mice, all recipients spontaneously developed histologically and serologically evident autoimmune diseases (such as thyroiditis, gastritis, insulitis, sialoadenitis, adrenalitis, oophoritis, glomerulonephritis, and polyarthritis); some mice also developed graft-vs-host-like wasting disease. Reconstitution of CD4+CD25+ cells within a limited period after transfer of CD4+CD25- cells prevented these autoimmune developments in a dose-dependent fashion, whereas the reconstitution several days later, or inoculation of an equivalent dose of CD8+ cells, was far less efficient for the prevention. When nu/nu mice were transplanted with allogeneic skins or immunized with xenogeneic proteins at the time of CD25- cell inoculation, they showed significantly heightened immune responses to the skins or proteins, and reconstitution of CD4+CD25+ cells normalized the responses. Taken together, these results indicate that CD4+CD25+ cells contribute to maintaining self-tolerance by down-regulating immune response to self and non-self Ags in an Ag-nonspecific manner, presumably at the T cell activation stage; elimination/reduction of CD4+CD25+ cells relieves this general suppression, thereby not only enhancing immune responses to non-self Ags, but also eliciting autoimmune responses to certain self-Ags. Abnormality of this T cell-mediated mechanism of peripheral tolerance can be a possible cause of various autoimmune diseases.

/pdf/immunologic-self-tolerance-maintained-by-activated-t-cells-4ig5217vg5.pdf

Immunologic self-tolerance maintained by activated T cells expressing IL-2 receptor alpha-chains (CD25). Breakdown of a single mechanism of self-tolerance causes various autoimmune diseases.

We report here that cells co-purifying with mesenchymal stem cells--termed here multipotent adult progenitor cells or MAPCs--differentiate, at the single cell level, not only into mesenchymal cells, but also cells with visceral mesoderm, neuroectoderm and endoderm characteristics in vitro. When injected into an early blastocyst, single MAPCs contribute to most, if not all, somatic cell types. On transplantation into a non-irradiated host, MAPCs engraft and differentiate to the haematopoietic lineage, in addition to the epithelium of liver, lung and gut. Engraftment in the haematopoietic system as well as the gastrointestinal tract is increased when MAPCs are transplanted in a minimally irradiated host. As MAPCs proliferate extensively without obvious senescence or loss of differentiation potential, they may be an ideal cell source for therapy of inherited or degenerative diseases.

/pdf/pluripotency-of-mesenchymal-stem-cells-derived-from-adult-200s4qlizf.pdf

Pluripotency of mesenchymal stem cells derived from adult marrow

Xenogeneic immunizations have the advantage of detecting a wide range of antigenic determinants because many commonly occurring proteins have diverged significantly during the course of evolution and are thus antigenic in other species. The broadness of xenogeneic responses, however, means that the antisera they produce are usually complex and require extensive absorptions to make them specific for a single antigen. This problem has now been overcome by generating hybridomas producing monoclonal antibodies (Kohler & Milstein 1975). These permit dissection ofthe xenogeneic response so that large amounts of individual antibodies can be obtained, each of which recognizes only one of the determinants recognized by a broadly reactive conventional antiserum. Williams et al. (1977) used hybridoma monoclonal antibodies obtained after immunizations of mice with rat cells to study rat cell-surface antigens present on subpopulations of rat lymphocytes, i.e., differentiation antigens. Springer et al. (1978a) and Stern et al. (1978) used a similar approach to study mouse lymphocyte antigens. They prepared monoclonal antibodies by immunizing rats with mouse lymphocytes and showed that these monoclonals recognized previously undetected mouse cell surface determinants including a glycoprotein antigen that appears to be specific for macrophages (Springer et al. 1978b). Trowbridge (1978) also used rat anti-mouse immunizations to generate a monoclonal antibody against the non-polymorphic lymphocyte surface antigen T200.

Xenogeneic monoclonal antibodies to mouse lymphoid differentiation antigens.

The amino-acid sequence of one form of the receptor for nerve growth factor defines a new class of growth factor receptors.

Gene transfer and molecular cloning of the rat nerve growth factor receptor.

The ROSAβgeo26 (ROSA26) mouse strain was produced by random retroviral gene trapping in embryonic stem cells. Staining of ROSA26 tissues and fluorescence-activated cell sorter-Gal analysis of hematopoietic cells demonstrates ubiquitous expression of the proviral βgeo reporter gene, and bone marrow transfer experiments illustrate the general utility of this strain for chimera and transplantation studies. The gene trap vector has integrated into a region that produces three transcripts. Two transcripts, lost in ROSA26 homozygous animals, originate from a common promoter and share identical 5′ ends, but neither contains a significant ORF. The third transcript, originating from the reverse strand, shares antisense sequences with one of the noncoding transcripts. This third transcript potentially encodes a novel protein of at least 505 amino acids that is conserved in humans and in Caenorhabditis elegans.

https://www.pnas.org/content/pnas/94/8/3789.full.pdf

Disruption of overlapping transcripts in the ROSA βgeo 26 gene trap strain leads to widespread expression of β-galactosidase in mouse embryos and hematopoietic cells

We describe the biochemical properties and cell surface distributions of three human T cell antigens (Leu-1, Leu-2a, and Leu-2b) which we postulate to be the homologues of the Lyt-1, Lyt-2, and Lyt-3 antigens that distinguish functional T cell subsets in the mouse. Leu-l, like Lyt-1, is on all thymocytes and peripheral T cells and is present in greater amounts on the helper/inducer subset than on the cytotoxic/suppressor subset. Both antigens increase in parallel fashion during T cell maturation in the thymus and each antigen is carried on a single 67,000-molecular weight (relative) (M(r)) polypeptide chain. Surprisingly, Leu-1 and Lyt-1 each are also expressed in readily detectable amounts on some B celI Ieukemias but not detectably so on normal B cells. 

Leu-2a and Leu-2b are antigens found only on suppressor/cytotoxic cells in the human and are very similar to the murine Lyt-2 and Lyt-3 antigens. In both species, the two antigens are on the same disulfide- linked multimeric molecules. Disulfide-bond reduction in both species yields subunits of similar size and charge. Lyt-3 and Leu-2b are extremely sensitive to trypsin digestion on viable cells whereas Lyt-2 and Leu-2a are much less so. 

A different membrane antigen, Leu-3, is an exclusive marker of the helper/inducer subset in man. No mouse homologue for this 55,000-M(r) protein is known. 

The maintenance of the homologous molecules on functionally distinct T cell subpopulations in two evolutionarily distant species suggests that the Lyt and Leu antigens perform essential functions for the cells on which they are found.

https://rupress.org/jem/article-pdf/153/2/310/1091460/310.pdf

Evolutionary conservation of surface molecules that distinguish T lymphocyte helper/inducer and cytotoxic/suppressor subpopulations in mouse and man

Methods for producing functional immunoglobulin are provided. The methods involve transfecting and expressing exogenous DNA coding for the heavy and light chains of immunoglobulin. In some embodiments, chimeric immunoglobulins are provided having variable regions from one species and constant regions from another species by linking DNA sequences encoding for the variable regions of the light and heavy chains from one species to the constant regions of the light and heavy chains respectively from a different species. Introduction of the resulting genes into mammalian host cells under conditions for expression provides for production of chimeric immunoglobulins having the specificity of the variable region derived from a first species and the physiological functions of the constant region from a different species.

Leonard A. Herzenberg

Papers

Xenogeneic monoclonal antibodies to mouse lymphoid differentiation antigens.

Gene transfer and molecular cloning of the rat nerve growth factor receptor.

Disruption of overlapping transcripts in the ROSA βgeo 26 gene trap strain leads to widespread expression of β-galactosidase in mouse embryos and hematopoietic cells

Evolutionary conservation of surface molecules that distinguish T lymphocyte helper/inducer and cytotoxic/suppressor subpopulations in mouse and man

Methods and transformed mammalian lymphocytic cells for producing functional antigen-binding protein including chimeric immunoglobulin and fragments