Lymphocyte transformation induced by autologous cells. V. Generation of immunologic memory and specificity during the autologous mixed lymphocyte reaction.

Lymphocyte proliferation in vitro may follow antigen recognition and serve as a correlate of cell-mediated immunity. Lymphocyte proliferation can also be simulated by nonimmune mechanisms as, for example, following culture with plant lectin, lipopolysaccharides, or staphylococcal protein A (1). The autologous mixed lymphocyte reaction (MLR) refers to the proliferation of T lymphocytes cultured with autologous mon-T lymphocytes (2,3). The purpose of this study was to determine whether lymphocyte proliferation in the autologous MLR results from immune or nonimmune mechanisms. We have shown that the autologous MLR has two classical attributes of an immune phenomenon: memory and specificity.     

Effect of propranolol on platelet function.

Excessive reactivity of blood platelets may contribute to atherosclerotic vascular disease. Hence drugs which alter platelet function may be protective. Prompted by findings that propranolol therapy normalized hyperactive platelet aggregation in patients with coronary artery disease, we studied propranolol in vitro to assess its action on platelets. At concentrations similar to those achieved in vivo (0.1-1 muM), propranolol raised the thresholds for aggregation of some normal paltelets by adenosine diphosphate (ADP). At higher concentrations (10-50 muM), propranolol abolished the second wave of platelet aggregation induced by ADP and epinephrine, and inhibited aggregation induced by collagen, thrombin, and the ionophore A23187. Propanolol blocked the release of 14C-serotonin from platelets, inhibited platelet adhesion to collagen, and interfered with clot retraction. Propranolol blocked ionophore-induced uptake of 45Ca by platelets. Inhibition appeared unrelated to beta-adrenergic blockage, as d(+) propranolol (which lacks beta-blocking activity) was equipotent with 1(-) propranolol. Moreover, practolol, a beta-blockading drug which is nonlipophilic, did not inhibit platelet function. These studies suggested that propranolol, like local anesthetics, decreased platelet responsiveness by a direct action on the platelet membrane, possibly by interfering with calcium availability. Modulation of platelet function by propranolol may occur at concentrations achieved at usual clinical doses of the drug.     

Recovery of prostacyclin production by de-endothelialized rabbit aorta. Critical role of neointimal smooth muscle cells.

Prostacyclin (PGI2) synthetic capacity was assayed at the surface of aortas at various intervals after removal of endothelium with a balloon catheter. Results were correlated with morphologic changes in the vessel wall seen by light microscopy, scanning and transmission electron microscopy. To assay PGI2 synthetic capacity, we applied an incubation chamber to the luminal surface of the aortas; after arachidonic acid stimulation we assayed the PGI2 synthesized with a bioassay and radioimmunoassay. PGI2 synthesis in de-endothelialized aortas was determined immediately after balloon-catheter injury and at intervals of 1 h and 2, 4, 15, 35, and 70 d. PGI2 synthesis was low at 1 h and increased over time with levels at 35 and 70 d reaching that of normal artery. Scanning and transmission electron microscopy of de-endothelialized areas showed persistent absence of endothelium with formation of a neointima composed of smooth muscle cells. De-endothelialized aorta was covered with adherent platelets shortly after injury, however several days later only a few platelets adhered to the denuded surface. Results indicated that (a) endothelium is responsible for nearly all PGI2 production at the luminal surface of the normal aorta, (b) de-endothelialized muscular neointima synthesized increasing quantities of PGI2 with time after injury, and (c) increase of PGI2 production at the luminal surface of de-endothelialized aorta correlates with formation of a neointima and with the acquired thromboresistance of the aorta.     

Effects of low dose aspirin on platelet function in patients with recent cerebral ischemia

We tested the antiplatelet effects of low-dose aspirin in patients with occlusive cerebrovascular disease, because conventional dosage aspirin inhibits vascular synthesis of prostacyclin at the same time that it inhibits platelets. The effects on platelet function and thromboxane A2 synthesis of 40 mg of aspirin daily or 40 mg aspirin plus dipyridamole were measured in 23 patients starting within a week after the onset of cerebral ischemia. All patients had normal baseline platelet aggregation responses to four stimuli: arachidonate, epinephrine, adenosine diphosphate and collagen. The generation of thromboxane A2 by platelets, measured as serum thromboxane B2, was also normal. After 3 to 7 days of low dose aspirin therapy, platelet aggregation responses were suppressed to the extent observed with higher dosage aspirin. Serotonin release during platelet aggregation was inhibited by more than 95% and thromboxane B2 levels in clotted blood fell by more than 95%. Responses to aspirin treatment were similar in patients with transient ischemic attacks and in those with stroke and were also similar in both sexes. No differences in platelet responses were observed between patients receiving aspirin alone and aspirin plus dipyridamole. Thus 40 mg aspirin daily inhibited platelet responses as effectively as higher doses of aspirin in patients who had recent cerebral ischemia and showed a cumulative antiplatelet effect.     

Response to therapy in IgG myeloma patients excreting lambda or kappa light chains: CALGB experience.

Sixty-eight previously untreated patients with IgG myeloma who were entered into five protocols of Cancer and Leukemia Group B (CALGB) were studied in order to determine the possible influence of excretion of kappa versus lambda urinary light chains on responses to treatment and survival. All patients in these protocols were included if the serum and urine protein abnormalities were confirmed by one of the two group reference laboratories. Pretreatment characteristics of the two groups of patients did not differ significantly. Of 44 patients with kappa Bence Jones proteinuria, 19 patients (43%) had good responses to treatment, whereas only 3 of 24 patients (13%) with lambda Bence Jones proteinuria had good responses (p = 0.02). Survival for the patients excreting kappa light chains was significantly better than survival for patients excreting lambda chains (median survival 31 versus 12 mo, p = 0.02).     

Old mice recover the ability to produce IgG and high-avidity antibody following irradiation with partial bone marrow shielding.

The splenic plaque-forming-cell (PFC) response to trinitrophenylated bovine gamma globulin of 18- to 20-month-old mice is markedly depressed, with a preferential loss of indirect (IgG) PFC and high-avidity-antibody-secreting cells compared to 6- to 8-week-old animals. The anti-trinitrophenyl response of old mice, whose peripheral lymphoid system has been reconstituted from their own bone marrow after irradiation while their bone marrow was partially shielded, includes high-avidity and IgG PFCs relatively comparable to those of normal young mice. If young mice are irradiated while their bone marrow is partially shielded and given purified splenic T cells from either old or young donors during recovery from irradiation, then the avidity distribution and the ratio of IgG/IgM PFCs they produce in response to trinitrophenylated bovine gamma globulin reflects the characteristic immune response of the T-cell donor. These results are consistent with the hypothesis that the bone marrows of old and young mice are similar with regard to the spectrum of B-cell clones that they can generate and that it is peripheral regulatory effectors that are responsible for much of the age-related change in the immune response. In addition, if one calculates the PFC avidity distribution taking into account those cells whose secretion of antibody was inhibited by anti-idiotype autoantibodies, then it is clear that there are more high-avidity B cells present in old mice than are detected by the conventional plaque-inhibition assay. Thus, the reduced avidity of the PFC response of old mice appears to be, at least in part, due to down regulation by anti-idiotype autoantibodies.     

Abrupt propranolol withdrawal in angina pectoris: effects on platelet aggregation and exercise tolerance.

Data collected before the initial reports of myocardial infarction following sudden withdrawal of propranolol are presented here to evaluate possible mechanisms for this phenomenon. Twenty patients with angina pectoris were randomized into placebo and propranolol (160 mg./day) treated groups and followed for 50 weeks at which time treatment was abruptly discontinued. Measurements of exercise tolerance, the product of heart rate and blood pressure at exercise end-point (HR × BP), and platelet aggregation thresholds in response to ADP and epinephrine were made before, during, and after treatment. Prior to propranolol, mean total work performance was 765 ± 125 k.p.m., HR × BP (heart rate-blood pressure product) was 16,800 ± 1,535. Mean platelet aggregation threshold with ADP was 1.32 μM¹; with epinephrine 1.26 μM¹. Patients treated with propranolol demonstrated significant improvement in exercise performance (1,790 ± 285 k.p.m., p < .01), reduction in HR × BP (12,000 ± 895, p < .01), and an elevation in platelet aggregation threshold; with ADP 3.43 μM¹ (p < .01); with epinephrine 12.9 μM¹ (p < .01). Following abrupt cessation of propranolol, exercise tolerance and HR × BP fell below pretreatment levels (630 ± 117 k.p.m. and 15,500 ± 513, respectively). Similarly platelet aggregation threshold fell to 1.0 μM¹ with ADP and 0.57 μM¹ with epinephrine. In six patients platelets were significantly more hyperaggregable than prior to therapy. Anginal frequency increased in all, but no acute infarction was observed. Abrupt withdrawal of propranolol may be deleterious in patients, sometimes causing “rebound” platelet hyperaggregability associated with increasing anginal frequency and decreasing exercise tolerance.