Synthesis and cell surface display of class II determinants by long-term propagated rat T line cells

We have investigated the capacity of the encephalitogenic BS rat T cell line bs 83 and its variant clone bs 83.III.C6 to synthesize and express RT1.B-specific class II molecule subsets defined by monoclonal antibodies (mAb) MRC-OX6 and MRC-OX3. Earlier studies had indicated that mAb MRC-OX6 recognizes three distinct molecular species: an immature oligomeric polypeptide chain complex comprised of the polymorphic subunits alpha, beta and the invariant proteins of the gamma group; a biosynthetic intermediate composed of post-translationally modified alpha, beta and gamma chain (denoted p35) and a fully glycosylated alpha, beta two-chain complex derived from the plasma membrane. MRC-OX3 was shown to recognize a serologically distinct alpha, beta two-chain complex that coexists with the MRC-OX6-specific heterodimer at the cell surface. Here we show that premutant bs 83 cells were unable to synthesize class II molecules of either set. In contrast endogeneous synthesis by mutant cells of MRC-OX6-specific molecules was demonstrated. Unlike control spleen cells variant cells failed to synthesize the mature MRC-OX3-reactive class II subset. Instead a three-polypeptide chain complex comprised of the terminally glycosylated subunits alpha, beta and invariant chain p35 was present at the cell surface. This complex appears to represent the preserved biosynthetic intermediate that failed to release invariant chain p35 upon its transit into the plasma membrane. These latter observations support our notion of gamma chain-induced epitope diversification during post-translational maturation of RT1.B-specific class II molecules.

Inhibition of replication of the etiologic agent of acquired immune deficiency syndrome (human T-lymphotropic retrovirus/lymphadenopathy-associated virus) by avarol and avarone

Avarol and avarone are two antimitotic and antimutagenic agents that preferentially inhibit proliferation of T-cell leukemia lines in vitro. This report shows that these compounds have a dose-dependent inhibitory effect on the replication of the etiologic agent of acquired immune deficiency syndrome (AIDS), human T-lymphotropic retrovirus (HTLV-III)/lymphadenopathy-associated virus, in human H9 cells in vitro. Both compounds show a significant cytoprotective effect on HTLV-IIIB-infected H9 cells at concentrations as low as 0.1 microgram/ml (0.3 microM). Both avarone and avarol block in a dose-dependent manner the expression of the p24 and p17 gag proteins of HTLV-III in H9 cells after virus infection and block viral replication, as judged by approximately 80% inhibition of reverse transcriptase activity. These results strongly suggest that these compounds may prove to be useful in the treatment of patients with AIDS and AIDS-related complex.

Calmodulin: localization in plant tissues

Calmodulin was purified from bovine brain by preparative SDS-polyacrylamide gel electrophoresis. The denatured, purified calmodulin was used to immunize rabbits to produce antiserum. This antiserum was used to study the distribution of calmodulin in plant tissues by indirect immunohistochemistry. The root tips from corn seeds, oat seeds, peanuts, spaghetti squash seeds, and the terminal buds of spinach were investigated. A method for plant tissue sectioning and inhibition of endogenous peroxide activity was developed. In the corn root section, reaction product from anti-calmodulin was found mainly in the root cap cells. Lesser but significant amounts of calmodulin were localized in metaxylem elements, in some stele cells surrounding metaxylem elements, in apical initials, and in the cortical cells. Similar findings were also observed in other root tips from oat seeds, peanuts, and spaghetti squash seeds. In the terminal buds of the spinach, calmodulin-stained cells were highly concentrated in the apical meristem and leaf primordium. These findings suggest that the high concentration of calmodulin in the root cap may be important in relation to gravitropism and growth development.

Ia-restricted encephalitogenic T lymphocytes mediating EAE lyse autoantigen-presenting astrocytes

T lymphocytes specific for myelin basic protein (MBP) are responsible for the cellular events leading to autoimmune disease within the central (CNS) and peripheral (PNS) nervous systems. Both in actively induced and T-cell transfer versions of experimental autoimmune encephalomyelitis (EAE) and neuritis (EAN), the autoaggressive T cells are activated outside the nervous system and reach their target tissue via the blood circulation. The target specificity of the autoaggressive T cells is impressive; T-cell lines specific for MBP predominantly home to and affect the white matter of the CNS whereas T cells specific for PNS myelin protein P2 exclusively infiltrate peripheral nerves. Having penetrated the tight blood tissue barriers, the lymphocytes seem to interact with local cells expressing the relevant autoantigen in an immunogenic form. Although the exact mechanism of target finding and destruction is unknown, studies from our laboratory have shown that astrocytes, a main component of the normal CNS glia, can actively present antigen to specific T cells. This observation suggests that astrocytes are involved in natural immune reactivity within the CNS, and that they may be involved in pathological aberrations, such as in the development of autoimmune lesions. Having studied astrocyte/T-cell interactions in more detail, we discovered that encephalitogenic T-cell lines recognizing MBP on astrocytes will subsequently proceed to kill the presenting cells. Here we report that astrocyte killing follows the rules governing 'classical' T-cell-mediated cytolysis; it is antigen-specific, restricted by antigens of the major histocompatibility complex (MHC) and apparently contact-dependent. Our data suggest that the nature of the recognized antigenic epitope determines whether or not antigen recognition is followed by killing; moreover, killing of antigen-presenting astrocytes seems to be correlated with the capacity to transfer encephalomyelitis to normal syngeneic rats.

Clonal analysis of the population of chondrocytes from the Swarm rat chondrosarcoma in agarose culture

Chondrocytes from the Swarm chondrosarcoma, a transplantable rat tumor, have been difficult to maintain in tissue culture for extended periods due to a time-dependent alteration of the culture to a more fibroblastic phenotype. This feature precluded the use of these cultures to examine chronic conditions that may affect cell metabolism, and the homogeneity or heterogeneity of the tumor cells within the culture population could not be examined. Use of suspension culture in agarose stabilized the chondrocyte phenotype, permitting long-term culture. Clones of tumor chondrocytes were established in agarose and were examined over 2-3 weeks for evidence that the cells were accumulating a proteoglycan-rich extracellular matrix, as determined by positive staining by Alcian blue, and were undergoing cell division. Nearly 90% of the cloned cells exhibited a prominent extracellular matrix by day 7 of culture and greater than 99% did so by day 14. Cell division did not occur to any great extent until days 6-7 of culture. After this lag, the cells appeared to undergo logarithmic growth, with a cell generation time of about 12 days. By 20 days of culture, between 80 and 90% of the initial clones contained multiple cells, indicating that nearly all the cells were in, or had entered, the cell cycle. These results suggest that the chondrocytes from the rat chondrosarcoma form a homogeneous cell population with respect to their ability to synthesize an extra-cellular matrix and divide.

Suppressor mutations for crs mutants of Bacillus subtilis

Mutants of Bacillus subtilis which carried suppressor mutations for catabolite-resistance gene crsA47 were isolated from methylmethanesulfonate-treated cultures of GLU-47 (crsA47). The suppressor mutation, sca19, suppressed resistance of crsA47 mutant to glucose and other inhibitors of sporulation. Moreover, the suppressor mutation could restore the rate of growth and the level of IMP dehydrogenase and alkaline phosphatase of crsA47 mutant to the wild-type level. The scal19 mutation was also able to suppress catabolite resistance of other crs mutants. The map position of the sca19 mutation indicated that this mutation was an intergenic suppressor for the crs mutants. It was also found that an erythromycin-resistance mutation, eryl, could suppress the catabolite resistance of some of the crs mutants. Our results were discussed in relation to the importance of a proper state of metabolic activities and membrane functions during the initiation of sporulation.

Killer-cell lines derived from mouse thymus, resembling large granular lymphocytes and expressing natural killer-like cytotoxicity

Murine thymus cells were maintained in vitro with supernatant-factors derived from Concanavalin-A-stimulated spleen cells. After an initial phase of vigorous proliferation, large granular cells (GC), which were not observed in fresh thymus cell preparations, appeared in these cultures. GC, derived from C3Hf/Tif-, BALB/c-, and C57BL/10-thymus cultures, could be slowly expanded and have been maintained as increasingly homogeneous (oligoclonal) lines for up to six months. During this time, other types of thymus cells died or were diluted out. Thymic GC differ functionally and histochemically from macrophages and mast cells. They do not phagocytize zymosan particles, bind opsonized SRBC, express nonspecific esterases or contain detectable amounts of histamine. GC share many features with natural killer (NK) cells and large granular lymphocytes (LGL). One morphologically representative line (C3Hf/Tif) had the following surface phenotype: Thy-1+, Lyt-1-, Lyt-2-, H-2K+, I-A-, asialo Gm1+. GC bind peanut agglutinin (PNA) on their surface and contain azurophilic granules. These cytoplasmic granules are considerably larger than those in LGL. Cells of a GC line derived from mouse strain C3Hf/Tif (H-2k) lysed the NK-sensitive YAC-1 (H-2a) and EL-4 (H-2b), but not the NK-insensitive P815 cells.

Macrophages as cytotoxic effector cells

Cells of the mononuclear phagocyte system can be activated by lymphokines to both increased extracellular cytotoxicity against tumor targets and intracellular cytotoxicity against micro-organisms. In addition, these effector cells can kill antibody-coated target cells in an ADCC system. These two cytotoxic mechanisms can co-operate and act synergistically. Such an synergistic action is characterized by the specificity of the antibody which coats the target cells and not by the non-specific activation induced by high dosages of lymphokine. The lymphokine MCF has partially been purified and separated from a variety of other lymphokines. This purified material, when injected into mice intraperitoneally, activates the macrophages to strong cytotoxicity. Evidence obtained by the use of different rat anti-mouse macrophage monoclonal antibodies suggests that there exist different subpopulations of macrophage and that some of these subpopulations can be correlated to defined functions.

Functionally different subpopulations of mouse macrophages recognized by monoclonal antibodies

Four rat anti-mouse macrophage monoclonal antibodies are described. Three of them are highly specific for macrophages, and one cross-reacts with granulocytes. All 4 antibodies do not react with membrane antigens shared by all macrophages, but with antigens present only on subpopulations of 20-50% of the cells. All antibodies are directly or indirectly cytotoxic for macrophages. The subpopulations defined by these antibodies can be correlated with certain macrophage functions. Thus, antibody M 43 eliminates macrophages that are activated by lymphokine to cytotoxicity. Antibodies M 43 and M 57 eliminate macrophages that kill antibody-coated tumor targets, and clone 102 (strictly macrophage-specific) eliminates natural killer cells. Only M 143, reacting with 10-30% of macrophages, has not yet been correlated with any function. With the use of these antibodies, cells of the macrophage lineage with specific functions can be recognized and eliminated from a given population.