Expression of theta antigen on mouse thymocytes during the cell cycle

Summary Cells from normal mouse thymus were subdivided according to size and analysed for surface antigen expression, protein content and DNA expression and content. It could be shown, that the expression of theta-antigen followed protein accumulation in individual cells. Protein content on the other hand, was correlated with DNA synthesis even if it varied over a greater range.Only one subgroup of small non-DNA-synthesizing cells was calculated to have a higher density indicative of a more condensed state together with an increased surface antigen content. These cells might represent the G₀ state of the remnant proliferating population and most resembled the small cortical cells.     

Thy 1 expression in the brain of nude mice.

The expression and cell distribution of Thy 1 antigen was studied in the brain of both normal and athymic (nude) young adult mice of the BALB/c strain by immunochemistry. In nude animals Thy 1 fluorescence was less intense and less regularly distributed in the molecular layer of the cerebellum and hippocampus. Thy 1 content determined by ELISA was lower by 10-16% in the cerebellum and 20-25% in the olfactory bulbs of nude mice. The total wet weight of the brain was lower by 16% than in control animals; the deficit in body weight ranged from 34-45%. It is supposed that the changes in Thy 1 expression in nude animals are caused mainly by the underdevelopment of late developing brain regions due to thermoregulatory problems and other postnatal strains occurring in the mutants.     

Two distinct types of cell surface folic acid-binding proteins in Dictyostelium discoideum

Folic acid is degraded too fast by Dictyostelium discoideum to study binding of this ligand to cell surface binding proteins. Folate deaminase activity was inhibited in the presence of 3.3 × 10⁻⁴ M 8-azaguanine. This inhibitor enabled us to detect two folate binding proteins. One type bound folic acid and deamino-folic acid with the same affinity (K_0.5 = 3–6 × 10⁻⁷ M) and apparently negative cooperativity. Binding to only this type was observed if 8-azaguanine was omitted. The second type bound folic acid noncooperatively with K_d = 7 × 10⁻⁷ M. Deamino-folic acid did not compete even at a 1000-fold excess. This type may correspond to the chemotactic receptor.     

Brain and sperm cell surface antigen (NS-4) on preimplantation mouse embryos

Antiserum prepared in rabbit against 4-day-old mouse cerebellum (anti-NS-4 serum) reacts in the complement-mediated cytotoxicity test with unfertilized and fertilized mouse eggs, cleavage stage embryos, and cells of the trophoblast and inner cell mass of the mouse blastocyst. This activity is specifically removed by absorption of antiserum with adult mouse brain and epididymal sperm but not with adult liver, spleen, kidney, and thymocytes. The antiserum reacts most strongly with cells of the trophoblast and inner cell mass and, in order of decreasing reactivity, with four- to eight-cell stage embryos, zygotes, unfertilized eggs, and two-cell stage embryos.     

A new and morphologically distinct population of cavernicolous Poecilia mexicana (Poeciliidae: Teleostei)

The cave molly, Poecilia mexicana, from the Cueva del Azufre, a sulfur cave in Tabasco, Mexico, ranks among the best-studied cave fishes worldwide, despite being known from a single population only. Here we describe a newly discovered second population of cave-dwelling P. mexicana from a nearby, but mostly non-sulfidic cave (Luna Azufre). Despite apparent similarities between the two populations (such as reduced eye diameter and reduced pigmentation), a geometric morphometric analysis revealed pronounced morphological differentiation between the two cave forms.     

HIV-1 replication in the central nervous system occurs in two distinct cell types

Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system (CNS) can lead to the development of HIV-1-associated dementia (HAD). We examined the virological characteristics of HIV-1 in the cerebrospinal fluid (CSF) of HAD subjects to explore the association between independent viral replication in the CNS and the development of overt dementia. We found that genetically compartmentalized CCR5-tropic (R5) T cell-tropic and macrophage-tropic HIV-1 populations were independently detected in the CSF of subjects diagnosed with HIV-1-associated dementia. Macrophage-tropic HIV-1 populations were genetically diverse, representing established CNS infections, while R5 T cell-tropic HIV-1 populations were clonally amplified and associated with pleocytosis. R5 T cell-tropic viruses required high levels of surface CD4 to enter cells, and their presence was correlated with rapid decay of virus in the CSF with therapy initiation (similar to virus in the blood that is replicating in activated T cells). Macrophage-tropic viruses could enter cells with low levels of CD4, and their presence was correlated with slow decay of virus in the CSF, demonstrating a separate long-lived cell as the source of the virus. These studies demonstrate two distinct virological states inferred from the CSF virus in subjects diagnosed with HAD. Finally, macrophage-tropic viruses were largely restricted to the CNS/CSF compartment and not the blood, and in one case we were able to identify the macrophage-tropic lineage as a minor variant nearly two years before its expansion in the CNS. These results suggest that HIV-1 variants in CSF can provide information about viral replication and evolution in the CNS, events that are likely to play an important role in HIV-associated neurocognitive disorders.     

Association of mouse adenovirus-induced cell surface antigen(s) with histocompatibility antigens

The topological relationship on the mouse adenovirus (M-Ad)-infected cell surface between virus-induced specific cell surface(s) antigens and serologically defined major histocompatibility antigens (H-2) was analyzed by the cap formation technique. Rhodamine-isothiocyanate (RITC)-labeled anti-S serum failed to stain the surface of virus-infected lymphoid cells which were pretreated with anti-H-2 serum and fluorescein isothiocyanate (FITC)-labeled anti-mouse immunoglobulin serum (anti-M-Ig) to cap the appropriate H-2 antigens. Conversely, the capping of the S antigens by pretreatment with anti-S followed by FITC anti-M-Ig serum induced cocapping of H-2 antigens. The β₂ microglobulins (β₂m) were also shown to be cocapped with S antigens by anti-β₂m or by anti-S serum. The S antigens, however, did not cocap with mouse-immunoglobulins or Thyl. 2 antigens on virus-infected B or T lymphocytes, respectively. To further elucidate the molecular relationship between S and H-2 antigens, radio-iodinated virus-infected cells were solubilized with Nonidet P40 (NP40) and S antigens were precipitated with anti-S serum. When the precipitates were analysed with sodium dodecyl sulfate Polyacrylamide gel electrophoresis, two major peaks were seen at positions of molecules of about 45,000 and 12,000 daltons both of which corresponded with molecules which were observed when NP40 extracts of virus-infected or uninfected cells were precipitated with anti-H-2 serum. Sequential immunoprecipitation analysis of infected cell extracts showed that S antigens were coprecipitated with either H-2K or H-2D antigens. These results suggest that the S antigens are somehow associated with H-2K or H-2D antigens separately.     

Characterization of a human B cell-specific antigen (B2) distinct from B1

A human B lymphocyte-specific antigen (B2) was identified and characterized by the use of a monoclonal antibody. By indirect immunofluorescence and quantitative absorption, B2 was shown to be expressed exclusively on Ig+ B cells isolated from peripheral blood and lymphoid tissues. In contrast, B2 was not found on monocytes, resting and activated T cells, Null cells, or granulocytes, nor was it found on cell lines or tumor cells of T cell or myeloid origin. Functional studies demonstrated that only B2 antigen-positive splenocytes could be induced to differentiate into plasma cells under the stimulus of pokeweed mitogen, further confirming the B cell specificity of B2. It was then demonstrated that the B2 antigen was distinct from the previously described B cell-surface determinants including surface immunoglobulin, Ia-like antigens, and Fc and C3 receptors. More importantly, the B2 antigen has been clearly shown to be distinct from the previously described B cell-specific antigen, B1, by its m.w. and expression on normal and malignant B lymphocytes. The distinct distribution of B2 on normal and malignant lymphocytes supports the notion of B cell heterogeneity and provides further evidence for existence of subpopulations of human B lymphocytes.     

Identification of a novel T cell surface disulfide-bonded dimer distinct from the alpha/beta antigen receptor

Hybridomas were prepared from the spleen of a BALB/c mouse immunized with EL-4 T lymphoma cells. One, designated A1, was found to secrete a monoclonal antibody that reacted with two T lymphoma cells of C57BL origin, EL-4 and C6VLB, but not with normal C57BL/6 splenocytes or thymocytes, C57BL/6 T cell clones, or other T or B lymphomas by complement-mediated cytotoxicity or indirect immunofluorescent staining. Monoclonal antibody (MAb) A1 precipitated a protein that migrated at 85 kD under nonreducing and 43 kD under reducing conditions. The fact that the antigen defined by MAb A1 was a disulfide-linked dimer, together with the essentially clone-specific distribution of the reactive epitope, raised the possibility that the antibody defined an epitope of the antigen receptor. However, several additional observations revealed that the antibody defined a distinct and novel T cell surface structure. MAb 124-40, previously shown to react with the antigen receptor of C6VLB cells, reacted with variants of C6VLB that failed to express the A1 epitope. Sequential immunoprecipitation indicated that MAb A1 and MAb 124-40 reacted with distinct molecular species on C6VLB cells. Endoglycosidase digestion showed that the structure reactive with MAb A1 was not derived from that reactive with MAb 124-40 by addition of N-linked oligosaccharide residues. Two-dimensional gel electrophoretic analysis of precipitates obtained from radioiodinated C6VLB cells with MAb 124-40 resolved the alpha and beta subunits of the antigen receptor. Similar analysis of precipitates obtained with MAb A1 revealed only a single basic chain under reducing conditions, although anomalous mobility suggestive of a second, more acidic chain was observed under nonreducing conditions. Two-dimensional maps of tyrosine-containing chymotryptic peptides of the proteins isolated with MAb A1 and MAb 124-40 were completely different, suggesting that the molecules shared no peptides and were distinct in primary structure. Finally, cross-linking studies performed with a cleavable reagent indicated that the A1 molecule, unlike the antigen receptor defined with MAb 124-40, was not associated with additional, T3-like structures on the surface of C6VLB cells. Although the MAb A1 was unreactive with normal cells in cytotoxicity or staining assays, a molecule of the appropriate size was immunoprecipitated in small amounts from lysates of radioiodinated normal spleen and thymus cells. These data indicate that MAb A1 defines a novel disulfide-linked T cell surface molecule distinct from the antigen receptor.     

Confidence intervals on the ratio of expected mean squares (theta 1 + d theta 2)/theta 3

The variance component ratio delta = (theta 1 + d theta 2)/theta 3 is of interest in many fields of application. This paper proposes and compares two methods for constructing confidence intervals on delta. The better method is compared with a method proposed by Graybill and Wang (1979, Journal of the American Statistical Association 74, 368-374) for the special problem of constructing an interval on sigma 2E/(sigma 2A + sigma 2B + sigma 2E) in a two-fold nested design. An example concerning a heritability study is provided.     

Brain-associated theta antigen: reactivity of rabbit anti-mouse brain with mouse lymphoid cells

Immunization of rabbits with mouse brain (which is known to contain Θ antigen) results in a potent anti-Θ-like antiserum. This antiserum termed “anti-brain-associated Θ”, BAΘ, is cytotoxic to thymus cells but not marrow cells, inhibits the primary in vitro response to RBC, does not affect antibody-forming cells which are of marrow origin, and inhibits the graft-versus-host reaction. It serves as a convenient means of obtaining large quantities of anti-thymus antiserum.     

E antigen (HBeAG) and surface antigen (HBsAg) in bladder schistosomiasis

The problem of the relationship between surface B antigen and schistosomiasis or other parasitic infections which are transmitted though the skin is not still resolved. Serum samples from 54 Somalian patients infected by Schistosoma haematobium were tested for the presence of the surface B antigen (HBsAg) and the e-antigen (HBeAg). The HbsAg was found in 14.8 per cent of these patients, while among controls (47 cases) the frequency was of 34.0 p]er cent; no e-antigen was found among the patients and controls, the prevalence of anti-HBs antibodies was of 57.4 per cent among the patients with urinary schistosomiasis and of 44.6 per cent among the controls; a low rate of anti-e antibodies was found in the patients (7.4%) and in the controls (10.6%). These observation seem to indicate that the problem of an increased frequency of hepatitis B virus markers among patients with urinary schistosomiasis needs for further investigation.