Separation and localization on sodium dodecyl sulfate polyacrylamide gels of pig spleen lymphocyte plasma membrane proteins which bind 125I-labelled phytohemagglutinin

The protein constituents of splenic pig lymphocytes derived from the plasma membranes, the endoplasmic reticulum or from a non-ionic (Nonidet P-40) detergent of whole cells have been separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, under reducing and non-reducing conditions. The binding of Phaseolus vulgaris (red kidney bean) phytohemagglutinin to these constituents has been studied by incubation of the labelled lectin with the undried electrophoretograms. Results show characteristic phytohemagglutinin-reactive components in each cell fraction, although the majority of the lectin-binding bands are common to the three fractions. Comparison of binding patterns for the reduced and non-reduced electrophoretograms does not reveal significant differences between the binding profiles. The components which bind the lectin in the largest amounts are located in the upper halves of the gels, which correspond to a molecular range of (75-250) . 10(3) daltons. Our data suggest that pig spleen lymphocyte plasma membranes contain at least 25-30 glycoproteins which can bind phytohemagglutinin. Iodine-labelled phytohemagglutinin binds to the vesicles prepared from lymphocyte plasma membranes and the Scatchard plot shows a non-linear upward concave curve.

Electrophoretic studies of the protein constituents of pig spleen lymphocyte plasma membrane and of a non-ionic detergent extract of intact cells

This report describes a study of the protein constituents of pig spleen lymphocyte plasma membrane, separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and analyzed under reducing and non-reducing conditions. The electrophoretic patterns of purified plasma membranes, of the endoplasmic reticulum fraction and of a non-ionic detergent (Nonidet P-40) extract of intact lymphocytes are compared. The lymphocytes were ruptured by the nitrogen cavitation method and the plasma membranes were purified by differential centrifugation in sucrose gradients. Plasma membranes were enriched in marker enzymes and appeared, in electron micrographs, as vesicles of various sizes and as fragmented membranes. The protein constituents were resolved into more than 60 bands which appeared, except in the endoplasmic reticulum fraction, as discrete Coomassie-positive bands. Characteristic bands were present in each of the three fractions when samples were not reduced. However, the majority of Coomassie-stained proteins migrated with the same relative mobility in all three fractions. Interestingly, all Coomassie-positive bands stained (some weakly) for glycoproteins. When samples were reduced and alkylated prior to electrophoresis, the electrophoretogram of each fraction differed from the non-reduced samples. In general, we observed that the fastest migrating portion of each gel was more intensively stained, when compared to non-reduced extracts. In addition, some bands characteristic of each fraction were evident, although most bands were common to each fraction. Coomassie-positive bands also stained with a glycoprotein staining reagent. Activity of alkaline phosphatase was demonstrated in the electrophoretograms of the non-reduced plasma membrane extracts. The results suggest that each of the three fractions analyzed under the conditions described here possesses a characteristic glycoprotein content. Furthermore, the data show that a Nonidet P-40 extract of lymphocytes is effective in solubilizing the glycoproteins from pig lymphocyte plasma membranes. Comparison of electrophoretic patterns with those reported for lymphocytes of other lymphoid organs of the pig suggests close similarities.

Binding of chemical derivatives of Phaseolus vulgaris phytohemagglutinin to pig spleen lymphocytes

The mitogenic activity of Phaseolus vulgaris phytohemagglutinin (PHA) and its acetyl, citraconyl, glycinyl, homoarginyl, N-bromosuccinimide, and nitro derivatives has been assayed using pig spleen lymphocytes. Nitrated and N-bromosuccinimide-treated PHA were not mitogenic. Whereas the mitogenicity of acetyl PHA was impaired, the other derivatives were as active as untreated lectin. Binding studies of [125I]PHA and derivatives to purified pig spleen lymphocytes were performed at 37 degrees C. Results show that the lymphocytes bound various amounts of lectin derivatives. Maximum amounts were observed in the case of mitogenic lectins. Data were analyzed by Scatchard plots and two kinds of binding sites were found for PHA and the mitogenic derivatives. High affinity and low affinity binding sites have been characterized in terms of (apparent) association constant and (apparent) number of sites. Binding of PHA or its chemical derivatives to a small fraction (4.6--9.0%) of all available lectin binding sites was sufficient for maximal lymphocyte stimulation. Nonmitogenic PHA derivatives (nitro or N-bromosuccinimide) bound, with low affinity, to one kind of binding site. The relevancy of these findings to lymphocyte activation is discussed.

Impairment by covalent modification of the ability of Phaseolus vulgaris phytohemagglutinin to stimulate cultured human lymphocytes: a comparison of different forms of covalent modification

Phytohemagglutinin (PHA) isolated from Phaseolus vulgaris has been modified by treatment with various chemical reagents and the modified proteins have been tested for their ability to stimulate peripheral lymphocytes from two healthy human donors, in vitro. Reaction of PHA with citraconic anhydride, S-methyl isothiourea, or 2-hydroxy-5-nitrobenzyl bromide produced derivatives which retained the ability to stimulate lymphocytes, at low concentrations. Acylation of the lectin with acetic anhydride or masking of the carboxyl side chains by reaction with glycinamide-carbodiimide impaired stimulation. When PHA was treated with N-bromosuccinimide or with tetranitromethane, the derivatives were ineffective as lymphocyte stimulants. Chemical modifications affected, in some cases, the quaternary structure of the lectin. Glycinamide-, homoarginine-, and nitro-PHA were tetramers whereas acetyl-, citraconyl-, and N-bromosuccinimide-treated lectin were dimers. Antinative lectin antiserum cross-reacted with all the modified proteins, except in the case of the N-bromosuccinimide derivative. The results show that, in the human lymphocyte transformation assay, the mitogenic property of PHA may depend on intact aspartic, glutamic, and tyrosine residues whereas lysine residues do not appear to be essential.

Studies on poison ivy. In vitro lymphocyte transformation by urushiol-protein conjugates

The isolation and purification of poison ivy urushiol is described. The preparation of urushiol-ski protein and urushiol human serum albumin is also described. Lymphocytes from eleven donor naturally sensitized to poison ivy and from four non-sensitive individuals have been cultured for 5 days in the presence of urushiol-carrier conjugates. Lymphocytes from seven of the eleven sensitive donors responded with a stimulation index greater than 3.0 to urushiol-albumin conjugate. When urushiol-skin protein conjugate was used as a stimulant, lymphocytes from only three of the eleven sensitive donors responded. The results suggest that urushiol-protein conjugates can stimulate sensitive lymphocytes in vitro, although a response is not observed in every individual naturally sensitized to poison ivy.

Toxic effect of alantolactone and dihydroalantolactone in in vitro cultures of leukocytes

Alantolactone, an allergenic sesquiterpene lactone, is toxic to leukocytes in in vitro cultures. Cell (1 X 10(6) cells/ml of culture) stimulation by pokeweed mitogen (PWM) decreases with increasing amounts of terpene. A concentration of 1 mug/ml of culture decreases stimulation by 50%. The reduced terpene, dihydro-11,13-alantolactone (DHA) is also toxic. A concentration of 1.7 mug/ml of culture of DHA brings about a 50% decrease in stimulation. Both compounds affect cell viability as measured by dye exclusion. It is suggested that the toxicity of alantolactone is not due to the presence of the alpha-methylene group conjugated to the carbonyl function of the gamma-lactone system.

The binding of phytohemagglutinin M to rat spleen lymphocytes. Quantitative studies

Phytohemagglutinin M (PHAM) has been purified from the commercial mixture of proteins produced by Phaseolus vulgaris, using a Sepharose-thyroglobulin column. The protein gave one band on gel electrophoresis and two bands on SDS-gel electrophoresis (mol. wt. 33 700 and 32 100, respectively). Molecular weight determination by ultracentrifugation gave a value of 61 200 +/- 700. The protein had a minimum sugar content of 16%. Binding studies of PHAM to purified rat spleen lymphocytes have been performed at 0, 25, and 37 degrees C. It was shown that the cells bound about the same amount of lectin at 0 and 37 degrees C, but less protein was bound at 25 degrees C. The binding phenomenon showed saturability at all temperatures. Data were analyzed by Scatchard plots and two kinds of binding sites were found. High-affinity sites and low-affinity sites have been characterized in terms of association constants and (apparent) number. It was also shown that cells treated with trypsin or sodium azide bound less lectin. Bound concanavalin A did not appear to affect the amount of bound PHAM, but its influence was reflected in the value of the association constant for the binding of PHAM. Unlabelled PHAM was shown to displace radioactive PHAM from the cells, but could not remove bound concanavalin A. The significance of these results is discussed in terms of the fluid plasma membrane model and cellular metabolism.

Reaction of alantolactone, an allergenic sesquiterpene lactone, with some amino acids. Resultant loss of immunologic reactivity

A study of the reaction of a hapten, alantolactone, with some amino acids is reported. Previously, we have reported than an α-methylene group attached to the γ-lactone is the immunologic requisite of alantolactone and some other sesquiterpene lactones. Such a group is known to be capable of undergoing "Michael-type addition" with the sulfhydryl group of cysteine. We confirm this finding and report that alantolactone can also undergo addition with the imidazole group of histidine and with the ε-amino group of lysine, but not with the guanido group of arginine, the hydroxyl group of serine, or the thio ether function of methionine. We selected these amino acids for further study because of their nucleophilic side chain. Samples of alantolactone that have undergone such addition no longer produce allergic eczematous contact dermatitis, as measured by patch test.

Cinnamylphenols as inhibitors of fungal growth

Cinnamylpyrogallol was found to be a greater inhibitor of fungal growth than either cinnamyl alcohol or pyrogallol. Antifungal activity decreased with time owing to oxidation of the compound in solution. Cinnamylphloroglucinol was less active than cinnamylpyrogallol against the 27 species of fungi (including dermatophytes) tested. In addition these substances also were active against two of the four bacterial species tested.