[Changes in immunocompetent cells under exposure to ionizing radiation]. / Izmeneniia immunokompetentnykh kletok pod vozdeistviem ioniziruiushchei radiatsii.

The modern knowledge concerning radiosensitivity of immunocompetent cells and intracellular changes is discussed in the review. A conclusion is made about the results of irradiation which are not easy to interpret. They depend on the cell type, functional state, and some other factors and conditions. The situation must be taken into consideration when developing the problem about treatment of post-irradiation changes.

Effects of low-doses of X-rays on the expression of human cell surface CD2 antigen in CD2+ CHO cells.

Thioguanine resistant CHO cells (HPRT-) were stably cotransfected with pSV2-gpt and pi H3-CD2 vectors using the calcium phosphate coprecipitation technique. The effects of single low doses of ionizing radiation were studied in a CD2+ CHO clone. The CD2+ phenotype responsible for binding sheep erythrocytes and rosette formation, was not affected by X-rays doses in the range 2-6 cGy. However, after 10 cGy of X-irradiation, 50% of the cells lost the CD2+ phenotype. These results suggest that this CD2+ clone might be a very sensitive indicator of very low X-ray doses. The implications of the phenotypic changes, observed after very low doses of irradiation, are discussed.

Photoaffinity labelling and radiation inactivation of the leukotriene B4 receptor in human myeloid cells.

The leukotriene (LT) B4 receptor has been characterized in the human monocyte leukemia THP-1 cell line. Scatchard analysis of [3H]LTB4 specific binding to THP-1 cell membranes revealed a single population of high affinity (KD = 56 pM) and saturable (2000 receptors/cell) binding sites. [3H]LTB4 specific binding was enhanced by divalent cations, but inhibited by both monovalent cations and a non-hydrolysable GTP analogue. Treatment with GTP analogue resulted in a concentration-dependent reduction in the number of high affinity binding sites, accompanied by the appearance of an equal number of binding sites of lower affinity (KD = 1250 pM). In contrast, Scatchard analysis with human polymorphonuclear leukocyte (PMN) membranes consistently revealed two populations of LTB4 receptors (KD = 48 pM and 270 pM). Treatment with GTP analogue, however, converted all these detectable binding sites to the lower affinity state. These data suggest that the LTB4 receptor in both THP-1 cell and PMN membranes exists in interconverting affinity states modulated by G-protein coupling. The similarity between the LTB4 receptors present in these two cell types was also substantiated by target-size analysis by radiation inactivation, which estimated a comparable molecular mass of 56.5 kDa and 52.8 kDa for the THP-1 cell and PMN LTB4 receptors, respectively. Finally, the presence of a single LTB4 receptor in PMN was demonstrated by direct photolabelling. Irradiation of frozen [3H]LTB4 equilibrium binding assay incubations resulted in complete photolysis of [3H]LTB4. Subsequent resolution of the tritiated PMN proteins by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis (PAGE) revealed one major radioactive peak migrating with an apparent molecular weight of 61,000. This peak was identified as the LTB4 receptor since radiolabelling could be completely inhibited by the presence of excess unlabelled LTB4 or the LTB4-receptor antagonist, L-662,328. Photolabelling was also partially inhibited by pretreatment with GTP analogue, consistent with G-protein uncoupling reagents reducing receptor affinity without complete inhibition. In summary, the LTB4 receptor identified in human myeloid cells is a G-protein coupled receptor with interconvertible high and low affinity states, having a molecular mass of 53-61 kDa.

Changes of CD2 receptor density determined by electron microscopy on blood lymphocytes following radiation treatment for breast cancer.

Changes of relative CD2 receptor on lymphocytes were examined in 11 women following radiation treatment for breast cancer by electron microscopy using antibody-coated gold particles. Proportions of blood lymphocytes with a high density of CD2 receptors were reduced, whereas those with no or a low density of such receptors were increased after radiation treatment.

Functional and physical molecular size of the chicken hepatic lectin determined by radiation inactivation and sedimentation equilibrium analysis.

Radiation inactivation and sedimentation equilibrium analysis were used to determine the functional and physical size of the chicken hepatic membrane receptor that binds N-acetylglucosamine-terminated glycoproteins. Purified plasma membranes from chicken liver were irradiated with high energy electrons and assayed for 125I-agalactoorosomucoid binding. Increasing the dose of ionizing radiation resulted in a monoexponential decay in binding activity due to a progressive loss of binding sites. The molecular mass of the chicken lectin, determined in situ by target analysis, was 69,000 +/- 9,000 Da. When the same irradiated membranes were solubilized in Brij 58 and assayed, the binding protein exhibited a target size of 62,000 +/- 4,000 Da; in Triton X-100, the functional size of the receptor was 85,000 +/- 10,000 Da. Sedimentation equilibrium measurements of the purified binding protein yielded a lower limit molecular weight of 79,000 +/- 7,000. However, the solubilized lectin was detected as a heterogeneous population of oligomers with molecular weights as high as 450,000. Addition of calcium or calcium plus N-acetylglucosamine decreased the higher molecular weight species, but the lower limit molecular weights remained invariant. Similar results were determined when the chicken lectin was solubilized in Brij 58, C12E9, or 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonic acid (CHAPS). Results from the present study suggest that in the plasma membrane, the functional species of the chicken hepatic lectin exists as a trimer. However, in detergent solution, the purified receptor forms a heterogeneous population of irreversible oligomers that exhibit binding activity proportional to size.

Soluble interleukin 2 receptors are released from activated human lymphoid cells in vitro.

With the use of an enzyme-linked immunoabsorbent assay to measure soluble human interleukin 2 receptors (IL 2R), certain human T cell leukemia virus I (HTLV I)-positive T cell lines were found to spontaneously release large quantities of IL 2R into culture supernatants. This was not found with HTLV I-negative and IL 2 independent T cell lines, and only one of seven B cell-derived lines examined produced small amounts of IL 2R. In addition to this constitutive production of soluble IL 2R by certain cell lines, normal human peripheral blood mononuclear cells (PBMC) could be induced to release soluble IL 2R by plant lectins, the murine monoclonal antibody OKT3, tetanus toxoid, and allogeneic cells. Such activated cells also expressed cellular IL 2R measurable in detergent solubilized cell extracts. The generation of cellular and supernatant IL 2R was: dependent on cellular activation, rapid, radioresistant (3000 rad), and inhibited by cycloheximide treatment. NaDodSO4-polyacrylamide gel electrophoresis analysis of soluble IL 2R released from either the HTLV I-positive T cell line HUT 102B2 or normal phytohemagglutinin-activated PBMC demonstrated molecules of apparent Mr = 35,000 to 40,000, and 45,000 to 50,000, respectively, somewhat smaller than the mature surface receptor on these cells. The release of soluble IL 2R appears to be a characteristic marker of T lymphocyte activation and might serve an immunoregulatory function during both normal and abnormal cell growth and differentiation.

Dose rate dependence of radiation induced IgG membrane receptor alteration [1].

Mouse lymph node lymphocytes are irradiated at different dose rates and the B-cell receptors to anti IgG are tested. The expression of receptors is inhibited by irradiation. It is shown that the effectivity of irradiation increases with decreasing dose rate suggesting that membrane damage may be important for situations of chronic irradiation or implant radiotherapy.

[Action of UV radiation on the surface of mammalian immunocompetent cells. I. Changes in the antigen and surface receptor expression of mouse spleen lymphocytes]. / Deistvie UF izlucheniia na poverkhnost' immunokompetentnykh kletok mlekopitaiushchikh. I. Izmenenie ékspressii nekotorykh antigenov i retseptorov poverkhnosti limfotsitov selezenki myshi.

Non-lethal and small lethal doses of short-wave (254 nm) and long-wave UV light (365 nm), the SUV and LUV rays, when acting upon the murine spleen cells, induce an increase in expression of the membrane markers of T-lymphocytes [theta-(Thy-I)-antigens] and B-lymphocytes (MBLA-antigens and EAC receptors). The sum of cells with T- and B-lymphocyte markers in an irradiated suspension is even more than the total amount of cells in a non-irradiated suspension (100%), which indicates the possibility of expression of those antigens and receptors of the plasmic membrane which are not revealed in non-irradiated lymphocytes. In the range of isolethal dosages (LD15-LD28) LUV irradiation suppresses, while that of SUV induces further increase of the expression of theta- and MBLA-antigens. From among the membrane markers of B-lymphocytes, the MBLA-antigens are more resistant against LUV and SUV irradiation than EAC-receptors.

Cytoplasmic requirements for the radio-induced modulation of IgG receptors on B-cells.

The effect of X-ray irradiation on IgG membrane receptors of B murine lymphocytes was studied. Cells were obtained from peripheral lymph nodes of RK mice and teased in Hank's solution. The cells were irradiated or kept as control samples, incubated at 37 degrees C, with or without drugs with known biochemical action at metabolic or structural levels, and labelled with fluorescein-conjugated anti-IgG antisera. The results show that X-ray irradiation results in a modulation of IgG receptor molecules on B-cells. The disappearance phase which takes only 10 min, is temperature dependent, and is prevented with metabolic inhibitors, microtubular disruptors, db-cAMP and local anesthetics. The re-appearance phase is also temperature dependent but apparently does not have either energy or cytoskeleton participation. The phenomenon is interpreted as partial and transient internalization of IgG molecules in the membrane.

Unexpected findings from target analysis of immunoglobulin E and its receptor.

The membrane receptor for immunoglobulin E (IgE) and its ligand, IgE, were irradiated with high-energy electrons. Loss of binding activity was measured for each, and the size of the functional targets was assessed. In both cases, the target size was substantially smaller than the covalent structure of the molecule. The direction of this discrepancy is unprecedented on the basis of experience with loss of enzymatic activity by irradiation; indeed, two enzymes which were present in the receptor preparations gave expected values when measured simultaneously. We suggest that in instances where a function such as ligand binding resides in a conformationally stable domain, radiation inactivation may be capable of revealing this.

Radiation induced loss of anti-Ig binding ability of lymphocytes.

The effect of irradiation on the anti Ig binding ability of lymphocytes after irradiation was studied. Normal control and irradiated lymphoid cells were treated with rabbit anti mouse IgG fluorescein conjugated serum and the fluorescein positive cells compared. A reduction in the proportion of stained cells in the irradiated lymphocytes was found. It depends on the dose and on the incubation time at 37 degrees C after irradiation. The maximum effect was detected after 10 minutes of incubation, longer incubation is associated with a partial recovery of the stainability of the IgG receptors.