Comparing long-term toxicity and efficacy of combined modality treatment including extended- or involved-field radiotherapy in early-stage Hodgkin's lymphoma.

BACKGROUND: To evaluate long-term toxicity and efficacy of a combined modality strategy including extended-field radiotherapy (EF-RT) or involved-field radiotherapy (IF-RT), the German Hodgkin Study Group carried out a follow-up analysis in patients with early unfavorable Hodgkin's lymphoma (HL). PATIENTS AND METHODS: One thousand two hundred and four patients were randomized to four cycles of chemotherapy followed by either 30 Gy EF- or 30 Gy IF-RT (HD8 trial); 532 patients in each treatment arm were eligible. RESULTS: At 10 years, no arm differences were revealed with respect to freedom from treatment failure (FFTF) (79.8% versus 79.7%), progression-free survival (79.8% versus 80.0%), and overall survival (86.4% versus 87.3%). Non-inferiority of IF-RT was demonstrated for the primary end point FFTF (95% confidence interval for hazard ratio 0.72-1.25). Elderly patients had a poorer outcome when treated with EF-RT. So far, 15.0% of patients in arm A and 12.2% in arm B died, mostly due to secondary malignancies (5.3% versus 3.4%) or HL (3.2% versus 3.4%). After EF-RT, there were more secondary malignancies overall (58 versus 45), especially acute myeloid leukemias (11 versus 4). CONCLUSION: Radiotherapy intensity reduction to IF-RT does not result in poorer long-term outcome but is associated with less acute toxicity and might be associated with less secondary malignancies.

A novel cytotoxic T lymphocyte activation assay. Optimized conditions for antigen receptor triggered granule enzyme secretion.

A method is described for the quantitative studies of cytotoxic T lymphocyte (CTL) activation. This functional assay is based on the measurements of secreted granule-associated enzymatic activity (BLT esterase (BLT-E) ) after incubation of CTL with activating stimuli. Immobilized mAb against CTL's antigen receptor (anti-TcR mAb), concanavalin A or a combination of PMA and ionophore A23187, were able to trigger the secretion of enzyme in the absence of target cells. Soluble anti-TcR mAb alone did not activate CTL, but using their conjugate with immobilized rabbit anti-mouse Ig antibody (RAMIg) TcR-mediated secretion of BLT-E was detected. Use of non-ionic detergents Nonidet P-40 or Triton X-100 (0.0125-0.2%) did not affect measurements of BLT-E activity. The efficiency of CTL exocytosis triggering by anti-TcR mAb which were immobilized on the surface of different plasticware is compared and conditions for studies of small and large numbers of CTL are described. The intensity of CTL response varies markedly with changes in buffer system, culture medium, additions of proteins. The optimal conditions for TcR complex triggered activation of murine CTL are described. Intensity of secretion can be easily manipulated by changing the surface density of immobilized anti-TcR mAb, thereby providing the possibility to screen inhibiting or activating agents (drugs or mAb) at selected sub-optimal levels of CTL activation. The potential for the use of described assay in screening of hybridoma supernatants for the presence of activating or inhibitory mAb against CTL's surface proteins is discussed. Since BLT-E secretion reflects exocytosis of granules from CTL, the conditions described here could be used for the detection of secretion of other markers of granules in future modifications of granule exocytosis assay.

Detection of distinct sets of newly synthesized polypeptides in supernatants of TCR-triggered T cell clones. Implication for the search for new lymphokines.

Using metabolic radiolabelling of proteins, which are newly synthesized during TCR-triggered T cell activation we were able to visualize distinct patterns of secreted polypeptides (with molecular weights ranging from 6 to 44 kDa) in supernatants of different T helper-1, T helper-2 and cytotoxic T cell clones. Most of these detected proteins are secreted in response to TCR-crosslinking (or to combined action of PMA and A231287), in an extracellular Ca(2+)-dependent manner and their appearance in supernatants was completely blocked by the addition of RNA synthesis or protein synthesis inhibitors or EGTA. Cyclosporin A (CsA) blocks secretion of several detected polypeptides, but does not affect TCR-triggered synthesis and secretion of others reflecting the existence of TCR-triggered, CsA-insensitive protein synthesis and secretion pathway. The insensitivity of secretion of several easily detectable polypeptides to inhibition by CsA offers a promising approach to further define the CsA-resistant and calcineurin-independent molecular pathways of TCR-triggered T cell activation. Several lymphokines (e.g., interferon-gamma, tumor necrosis factor, interleukin-4 and interleukin-10) are identified among the visualized set of secreted polypeptides. Since other, yet unidentified, secreted polypeptides in the same set of secreted proteins share important properties with known lymphokines it seems promising to use described approach in search for new lymphokines.

Induction of a graft-versus-leukemia reaction by cyclosporin A withdrawal as immunotherapy for leukemia relapsing after allogeneic bone marrow transplantation.

We studied the immunomodulating effect of withdrawal of immunosuppression with cyclosporin A (CsA) in 42 patients with leukemic relapse of chronic myelogenous leukemia (CML) (n = 24), acute myeloid leukemia (AML) (n = 13) and acute lymphoblastic leukemia (ALL) (n = 5) after allogeneic unmanipulated bone marrow (BMT) or peripheral blood stem cell transplantation (PBSCT). Response to CsA withdrawal was monitored molecularly by the polymerase chain reaction for elimination of CML cells containing the bcr-abl messenger RNA (mRNA) transcript (n = 24), or mll-af4 mRNA transcript characteristic of leukemic cells with a 11q23 chromosomal abnormality (n = 1). Rapid tapering of CsA resulted in subsequent achievement of cytogenetic remission in 11 of 14 CML patients (79%) who relapsed in early disease phase (n = 9 cytogenetic relapse, n = 2 hematological relapse) after a median of 57 days. Three of 13 AML patients and one of five ALL patients achieved complete remission. CsA withdrawal was accompanied by the development of acute graft-versus-host disease (GVHD) grade II in most of the 24 patients with CML. Two patients who achieved remission of AML or ALL died from severe GVHD grade III-IV. We calculated a probability of 84% for achieving and remaining in remission with early relapse of CML 4 years after relapse post BMT, whereas patients with AML have only a probability of about 10% of achieving and remaining in remission after 3 years. Patients with advanced CML and ALL had no chance of achieving and remaining in remission in the same time period.

Cyclic AMP-dependent protein kinase as a part of the possible down-regulating pathway in the antigen receptor-regulated cytotoxic T lymphocyte conjugate formation and granule exocytosis.

Screening activities of cytotoxic T lymphocytes (CTL) are viewed as a cycle of engagements and disengagements with target cells. One of the unexplained features of CTL activation is a biochemical mechanism of an "off" signal, which would result in disengagement of CTL from the target cell and termination of exocytosis of granules. Data are presented that suggest that cAMP dependent-protein kinase (PK-A) inhibits both early and late stages of antigen receptor-regulated CTL activation and may be a part of such an off signaling pathway.

HIV-related non-Hodgkin's lymphoma: CHOP induction therapy and interferon-alpha-2b/zidovudine maintenance therapy.

In a prospective multicenter study 68 out of 158 patients with HIV infection and malignant lymphoma were assigned to a risk-adapted induction therapy using the following algorithm: High-risk patients fulfilled 2 of 3 criteria: T4 lymphocytes <50/microL; WHO activity index 3 or 4; pre-existing AIDS-defining opportunistic infection. Normal-risk patients received 4 to 6 cycles of CHOP chemotherapy; those that achieved complete remission (CR) received zidovudine (500 mg/d) and interferon-alpha maintenance therapy (5 million units three times a week) for one year. High-risk patients received low-dose CHOP or vincristine/prednisone chemotherapy. Supportive care was performed with pentamidine inhalation and G-CSF. Intrathecal (it) methotrexate was given for CNS prophylaxis. The median survival was 634 days for 38 patients of the normal-risk group and 129 days for 30 patients of the high-risk group. 18 high-risk patients treated with low-dose CHOP had better survival (156 days) than 12 patients treated with vincristine/prednisone (72 days p=0.044). 68% of the patients in the normal-risk group achieved complete remission. 5 out of 18 high-risk patients treated with low-dose CHOP achieved complete remission. Three normal-risk patients developed fatal opportunistic infections during chemotherapy. Immune parameters deteriorated after CHOP induction and partially recovered with maintenance treatment. We conclude that the normal-risk patients survived longer than reported in most published studies. Toxicity was low. Low-dose CHOP seems to be superior to vincristine/prednisone therapy in high-risk patients.

Use of various diagnostic methods in a patient with Gaucher disease type I.

A series of plain radiographs, bone scans, bone marrow scans, and MRIs is reported in a patient with Gaucher disease type I, in whom two episodes of acute bone crisis developed during a 6-year period of follow-up. Acute bone crisis and global indolent bone marrow displacement could both be assessed by bone marrow scintigraphy, whereas MRI could better clarify the corti-comedullary alteration after bone infarction. Thus, MRI and bone marrow scintigraphy could be used as complementary imaging methods in the management of patients with Gaucher disease.

Poorer outcome of elderly patients treated with extended-field radiotherapy compared with involved-field radiotherapy after chemotherapy for Hodgkin's lymphoma: an analysis from the German Hodgkin Study Group.

BACKGROUND: The optimal treatment of elderly patients with Hodgkin's lymphoma (HL) is still a matter of debate. Since many of these patients receive combined modality treatment, we evaluated the impact of different radiation field sizes, that is extended-field (EF) or involved-field (IF) technique when given after four cycles of chemotherapy. PATIENTS AND METHODS: In the multicenter HD8 study of the German Hodgkin Study Group, 1204 patients with early-stage unfavorable HL were randomized to receive four cycles of chemotherapy followed by either radiotherapy (RT) of 30 Gy EF + 10 Gy to bulky disease (arm A) or 30 Gy IF + 10 Gy to bulky disease (arm B). A total of 1064 patients were assessable for the analysis. Of these, 89 patients (8.4%) were 60 years or older. RESULTS: Elderly patients had a poorer risk profile. Acute toxicity from RT was more pronounced in elderly patients receiving EF-RT compared with IF-RT [World Health Organization (WHO) grade 3/4: 26.5% versus 8.6%)]. Freedom from treatment failure (FFTF, 64% versus 87%) and overall survival (OS, 70% versus 94%) after 5 years was lower in elderly patients compared with younger patients. Importantly, elderly patients had poorer outcome when treated with EF-RT compared with IF-RT in terms of FFTF (58% versus 70%; P = 0.034) and OS (59% versus 81%; P = 0.008). CONCLUSION: Elderly patients with early-stage unfavorable HL generally have a poorer risk profile and outcome when compared with younger patients. Treatment with EF-RT instead of IF-RT after chemotherapy has a negative impact on survival of elderly patients and should be avoided.

Functional and biochemical characterization of a calcium-ionophore-induced state of unresponsiveness in a cytolytic T cell clone.

To characterize the requirements for the induction of an anergic state in immunocompetent cells we examined the effect of an increase in intracellular calcium concentration on the subsequent responsiveness of cytolytic T cells to antigenic stimulation in vitro. Pretreatment of a murine cytolytic T cell clone with the calcium-ionophore A23187 resulted in the induction of an anergic state characterized by a decrease in cytolytic activity and granule exocytosis upon Ag-specific stimulation. Furthermore, IFN-gamma synthesis declined whereas de novo synthesis of a yet unidentified protein with a molecular mass of 33 kDa as well as proliferative response of cells in response to exogenous IL-2 were unaffected. This state of partial unresponsiveness 1) could be prevented by concomitant pretreatment of cells with cyclosporin A or protein synthesis inhibitors and 2) was reversible within 48 h. Biochemical analysis of TCR-induced intracellular activation revealed a block in signal transduction before the activation of protein kinase C because cellular unresponsiveness could be bypassed by the phorbol ester PMA plus the calcium-ionophore A23187. However, phosphatidylinositol turnover was markedly inhibited in unresponsive cells that also did not show a calcium influx on stimulation with concanavalin A. We conclude that a rise in intracellular calcium in cytolytic T cells might not only be necessary for cellular activation but may also trigger the induction of a partial unresponsiveness to antigenic stimulation due to an inhibition in the early phase of signal transduction.

[Echinococcosis - a rare differential diagnosis of a tumorous hepatic lesion]. / Echinokokkose - seltene Differenzialdiagnose einer malignitätsverdächtigen hepatischen Raumforderung.

We report the case of a 44-year-old woman who was admitted to our hospital because of a newly developed painless jaundice. Though she felt quite well sonographic and radiographic evaluation showed a tumor of the liver. An extensive diagnostic workup was performed but it was not until laparotomy that a malignant tumor could definitely be ruled out and the presumptive diagnosis of an echinococcosis was proven. A partial resection of the liver was performed.

Differential effect of the activation of protein kinase A on the protein synthesis and secretion in the T-helper 2 cell line D10.G4.1.

The authors analysed the effect of protein kinase A (PKA) activation on the protein synthesis and secretion in the T-helper 2 cell line D10.G4.1 (D10) using an assay that allows the detection of almost all secreted proteins of a cell. IL-4 and IL-10 were quantified. Three groups of secretory products could be defined. The T-cell receptor (TCR)-induced production of the first group (A) of proteins including IL-4 was enhanced by low concentrations of PKA activators. At higher concentrations the enhancement was less marked. The synthesis and secretion of a second group (B) of proteins including IL-10 remained unaffected. The production of a third group (C) of proteins was inhibited in a concentration-dependent manner. Biochemical analysis revealed a block of phospholipase C gamma (PLC gamma) activity by PKA activators. When D10 cells were stimulated by a phorbol ester plus calcium ionophore the production of group A proteins was enhanced almost fourfold, whereas production of group B proteins was unaffected by PKA activation. This effect was observed at all concentrations of various PKA activators tested. The secretion of group C proteins was no longer inhibited. The same results were obtained when analysing IL-4 and IL-10 m-RNA by Northern blotting. The data demonstrate a lymphokine specific mode of action on a single cell basis. Furthermore, it suggests that the inhibitory action of PKA in D10 cells is due partly to blocking of PLC gamma activity.

Exocytosis of cytolytic granules may not be required for target cell lysis by cytotoxic T-lymphocytes.

Secretory processes have been implicated in the mechanism of target-cell lysis by cytotoxic T-lymphocytes (CTL) (refs 1, 2). Both CTL and cytotoxic large granular lymphocytes have cytolytic granules, containing the cytolytic molecules 'perforin' and 'cytolysin'; perforin and cytotoxic lymphocytes can damage target cells through the membrane assembly of pores. The description of proteases which are cytotoxic cell-associated and granule-located has supported the granule exocytosis model of cytotoxicity mediated by cytotoxic lymphocytes, and has emphasized the similarities between cell-mediated and complement-mediated cytotoxicity. But recent experiments have challenged the importance of lytic granules and perforin in CTL activity. Here we report that CTL can be triggered to deliver a lethal hit to target cells even when exocytosis of lytic granules has been abolished by removal of extracellular calcium. This dissociation of exocytosis of granules and delivery of the lethal hit suggests that cytolytic granules may not be involved in target-cell lysis by CTL.

[Transesophageal endosonographically-guided fine needle aspiration biopsy of mediastinal space-occupying lesions of uncertain importance]. / Die transösophageale endosonographisch gesteuerte Feinnadelaspirationsbiopsie mediastinaler Raumforderungen unklarer Dignität.

BACKGROUND AND OBJECTIVE: Endoscope-guided fine-needle biopsy of mediastinal space-occupying lesions is a recently introduced method of low invasiveness. This is a report of the authors' experience. PATIENTS AND METHODS: Between Nov. 1996 and April 1999 endoscope-guided mediastinal biopsies (Pentax FG 32 UA) were performed in 31 patients (eight women, 23 men; aged 27-80 years). The space-occupying lesion had to be less than 1 cm from the oesophagus and not more easily approachable in other ways. RESULTS: The method was successful in 23 of the 31 patients (74%). In ten of the 31 patients (32%) a malignant lesion was histologically proven. In six patients (19%) sarcoidosis was revealed. Of the eight patients with inadequate biopsy material a malignancy was ultimately diagnosed in three, sarcoidosis in one (in three by mediastinoscopy, in one by laparoscopy). Thus the sensitivity of diagnosing a malignancy was 77%, with a specificity of 100%. Follow-up examinations in the remaining four patients excluded a malignancy. CONCLUSION: Endoscope-guided fine-needle biopsy of mediastinal space-occupying lesions is a technically simple method causing little stress to the patient that can frequently elucidate the lesion's benignity or malignancy. Invasive procedures, such as mediastinoscopy, may thus be avoided in some patients.

Locus of inhibitory action of cAMP-dependent protein kinase in the antigen receptor-triggered cytotoxic T lymphocyte activation pathway.

The mechanism of the cAMP involvement in regulation of cellular functions was studied here using a novel functional assay (antigen receptor-triggered exocytosis of granules) of cloned cytotoxic T lymphocytes (CTL). We suggest that cAMP-dependent protein kinase, protein kinase A, counteracts the protein kinase C and Ca2+-mediated stimulatory T-cell antigen receptor (TcR)-triggered biochemical pathway. This suggestion is supported by experimental results which satisfy criteria for protein kinase A involvement in cellular functions. Pretreatment of CTL with cholera toxin induces cAMP accumulation in CTL, partially inhibits TcR-triggered "lethal hit" delivery to the target cell, and almost completely blocks TcR-triggered exocytosis of granules from CTL. Other agents that raise the intracellular level of cAMP, including forskolin and isobutylmethylxanthine (IBMX) also inhibit TcR-triggered CTL activation. Involvement of cAMP-dependent protein kinase in an inhibitory pathway is suggested by the synergistic effects of cyclic nucleotide analogs 8-bromo-cAMP and N6-benzoyl-cAMP in inhibition of TcR-triggered exocytosis. Forskolin and IBMX inhibited TcR-triggered phosphoinositide turnover in CTL, suggesting that cAMP affected very early events in signal transduction that follow TcR cross-linking by a ligand. The ability of IBMX to inhibit CTL activation when the TcR cross-linking step was by-passed by the combination of phorbol myristate acetate and ionophore A23187 suggests that the locus of inhibitory effect of cAMP is at both the early and late stages of the TcR-triggered transmembrane signaling pathway.

Extranodal mantle cell lymphoma mimicking marginal zone cell lymphoma.

AIM: We report a case of mantle cell lymphoma masquerading as a marginal zone cell lymphoma. METHODS AND RESULTS: In the initial manifestation in the palatine tonsils, the neoplastic cells were found to grow exclusively within the marginal zones of secondary follicles which showed a preserved mantle zone. The few immunostains performed showed a B-cell phenotype including an immunoglobulin light chain restriction. The extranodal manifestation, the growth pattern, and the immunophenotype led to the diagnosis of an extranodal marginal zone B-cell non-Hodgkin's lymphoma (NHL). The specimen from the relapse occurring 8 months later exhibited diffuse monomorphous cells co-expressing B-cell antigens and CD5, CD43 and cyclin D1, leading to the diagnosis of mantle cell lymphoma. Re-investigation of the initial biopsy revealed that the neoplastic cells within the marginal zones had a mantle cell lymphoma immunophenotype expressing cyclin D1, the immunoglobulin heavy chains IgD and IgM and partly CD5. Both lesions harboured identical clonal immunoglobulin gene rearrangements proving that they represented different manifestations of the same lymphoma. CONCLUSION: This case emphasizes the importance of broad immunohistological investigation of B-cell NHLs involving the marginal zone.

[Granulomatous hepatitis and myelitis: an unusual manifestation of extrapulmonary sarcoidosis]. / Granulomatöse Hepatitis und Myelitis: Ungewöhnliche Manifestation einer extrapulmonalen Sarkoidose.

Sarcoidosis is a chronic multisystem disorder of unknown cause characterized by the presence of noncaseating epitheloid granulomas and derangement of the normal skin architecture. Though an array of organs may be affected by the disease the most common site of affection is the lung. An extrathoratic manifestation is rare. We describe a 66-year-old patient who was admitted to our hospital because of weight loss and hepatomegaly. A thorough examination revealed the diagnosis of a granulomatous hepatitis characterized by a markedly elevated alkaline phosphatase concentration of 1,490 U/I. A drug-induced hepatitis could be excluded and no evidence was found for the existence of a bacterial or viral infection or an autoimmune disorder. An ERCP revealed a normal common bile duct and normally branching small intrahepatic ducts. The patient was discharged with the diagnosis of a biliary cirrhosis. Half a year later the patient was readmitted to the hospital because of severe intestinal bleeding due to pancytopenia. A bone marrow biopsy showed infiltration of the marrow by granulomas. A histiocytosis X could be ruled out. The diagnosis of an extrathoracic sarcoidosis was assumed and a therapy with prednisone was started. Within six weeks the blood count normalized. After 18 months the serum alkaline phospatase concentration also normalized and no granulomas were found in the bone marrow. The case demonstrates that pancytopenia in sarcoidosis is not due to bone marrow failure.

T cell antigen receptor triggered exocytosis in cytotoxic T lymphocytes is inhibited by soluble, but not immobilized monoclonal antibodies to Lyt-2 antigen.

The effect of monoclonal antibodies (mAb) to surface antigens on the T cell antigen receptor (TcR)-triggered exocytosis of intracellular granules in cytotoxic T lymphocytes (CTL) was studied. Soluble anti-LFA-1, anti-TcR, and anti-Lyt-2 mAb inhibited both CTL-inflicted 51Cr-release from the target cell (TC) and TC-stimulated exocytosis of granules from cloned CTL. Soluble anti-TcR and anti-Lyt-2 mAb but not soluble anti-LFA-1 mAb inhibited exocytosis, which was triggered by solid-phase anti-TcR mAb. Immobilized anti-Lyt-2 did not inhibit secretion triggered by immobilized anti-TcR mAb; immobilized anti-LFA-1 mAb had an modest inhibiting effect. Inhibition of exocytosis by soluble anti-Lyt-2 mAb was greater when stimulating anti-TcR mAb were immobilized at a lower density on a plastic surface. When the requirement for TcR cross-linking was bypassed by synergistic action of phorbol ester and ionophore A23187, no inhibition of exocytosis by soluble anti-Lyt-2 mAb was detected. The obtained data point to steric hindrance as the most likely explanation of the inhibition of TcR-triggered CTL activation by anti-Lyt-2 mAb.

Immunomodulating properties of a novel series of protein kinase C activators. The bryostatins.

Low concentrations of the protein kinase C activators, bryostatins 1 and 2 synergized with recombinant B cell stimulatory factor-1 in triggering differentiation (granule enzyme expression) and cytotoxic T lymphocyte (CTL) development in naive, resting lymph node T cells. Bryostatin greatly enhances efficiency of recombinant interleukin-2 in triggering development of in vivo primed CTL during in vitro incubation, thereby providing experimental evidence for the efficacious use of lower concentrations of recombinant interleukin-2 for in vivo tumor rejection studies. Both bryostatins 1 and 2 were able to trigger cytotoxicity of CTL clones against antigen-nonbearing target cells and inhibited CTL cytotoxicity against Ag-specific target cells. Bryostatin 1 and 2 synergize with Ca2+ ionophores in triggering the exocytosis of cytolytic granules from CTL at very low concentrations. In view of the lack of tumor promoting activity of the bryostatins, the possible use of these agents in vivo is discussed.

Age-associated T-lymphocyte activation through mitogens in patients with multiple sclerosis and blood donors.

In 128 patients with multiple sclerosis (MS) and 204 blood donors (control persons) the in vitro activation of 'Ficoll-purified' peripheral blood T lymphocytes was measured using the 3H-thymidine incorporation rate without (spontaneous proliferation) and with mitogen addition (concanavalin A, phytohemagglutinin). Mitogen responsiveness in control persons and MS patients decreased with age, reflecting a T-lymphocyte inherent mechanism for the diminution of responsiveness. The MS patients, ranging in age between 20 and 30 years, showed decreased mitogen responsiveness and a tendency to increased spontaneous proliferation compared to the control persons. These results could be an expression of a viral infection.

B cell stimulatory factor 1 (IL-4) enhances the development of cytotoxic T cells from Lyt-2+ resting murine T lymphocytes.

B cell stimulatory factor 1 (BSF-1) (IL-4) was shown to synergize with phorbol esters or with monoclonal anti-TCR antibody in stimulation of the development of CTL from small resting murine T cells. IL-2 also synergized with PMA in such differentiation but was less effective than BSF-1. The combination of these two lymphokines with PMA had the most potent effect on the development of CTL. BSF-1 plus PMA stimulated a significant increase in the intracellular content of N-benzyloxycarbonyl-L-lysine thiobenzylester esterase, a granule-associated biochemical marker, whereas IL-2 plus PMA was only marginally effective. Depletion of L3T4+ cells did not result in the abrogation of these effects. Lyt-2+ T cells that were incubated for 72 h with BSF-1 plus PMA accumulated N-benzyloxycarbonyl-L-lysine thiobenzylester esterase and secreted this intragranular marker after interaction with immobilized anti-T cell receptor mAb. These BSF-1/PMA-stimulated Lyt-2+, L3T4- T cells were also able to kill FcR positive target cells in a retargeting assay with a mAb to murine T3 Ag, providing evidence that BSF-1 plus PMA acted directly on precursors of cytotoxic T cells.