Final results of phase II trial of doxorubicin HCl liposome injection followed by bexarotene in advanced cutaneous T-cell lymphoma.

BACKGROUND: High response rates for doxorubicin HCl liposome injection (DLI) in cutaneous T-cell lymphoma (CTCL) have been reported with vague criteria until recently. Approximately 50% of CTCL patients respond to bexarotene (Bex). PATIENTS AND METHODS: A phase II trial was carried out to clarify the true overall response rate (ORR) for DLI and to assess the role of sequential Bex. Patients were treated with DLI 20 mg/m(2) i.v. every 2 weeks for 16 weeks (8 doses) followed by 16 weeks with Bex 300 mg/m(2) orally. Response assessments were carried out after 16 (DLI) and 32 weeks (Bex). Skin responses were measured by the modified Severity-Weighted Assessment Tool (mSWAT) and the Composite Assessment of Index Lesion Severity (CA). RESULTS: Thirty-seven patients were treated: stage IV (22, 8 with Sézary syndrome), IIB (10), earlier stage refractory to skin-directed therapies or radiation therapy (5). For 34 assessable patients: ORR 14/34 [41%: partial response (PR) 12, clinical complete response (CCR) 2]. Maximum responses were all seen after 16 weeks DLI. Median progression-free survival (PFS) was 5 months. There were 22 deaths: 21 of disease and 1 of heart failure. Twenty-seven grade 3 and 5 grade 4 toxic events were observed. CONCLUSION(S): With strict criteria, DLI ORR is among the highest reported for single agents in CTCL. Sequential Bex did not increase the response rate or duration.

Diverse spermatogenic defects in humans caused by Y chromosome deletions encompassing a novel RNA-binding protein gene.

We have detected deletions of portions of the Y chromosome long arm in 12 of 89 men with azoospermia (no sperm in semen). No Y deletions were detected in their male relatives or in 90 other fertile males. The 12 deletions overlap, defining a region likely to contain one or more genes required for spermatogenesis (the Azoospermia Factor, AZF). Deletion of the AZF region is associated with highly variable testicular defects, ranging from complete absence of germ cells to spermatogenic arrest with occasional production of condensed spermatids. We find no evidence of YRRM genes, recently proposed as AZF candidates, in the AZF region. The region contains a single-copy gene, DAZ (Deleted in AZoospermia), which is transcribed in the adult testis and appears to encode an RNA binding protein. The possibility that DAZ is AZF should now be explored.

Peracetic acid is effective for controlling fungus on channel catfish eggs.

Peracetic acid (PAA) is a relatively new compound suggested for use to treat pathogens in aquaculture. It is approved for use in Europe, but not in the United States. This study determined the effectiveness of PAA for fungus control on channel catfish, Ictalurus punctatus (Rafinesque), eggs. The study consisted of five PAA concentrations (2.5, 5, 10, 15 and 20mgL(-1) ) and an untreated control in a flow-through system. A single spawn was used for each replication (N =4). Eggs were treated twice daily until the embryos developed eyes. When hatching was complete for all viable eggs, fry were counted to determine the percent survival in each treatment. Fungal growth was severe in the untreated controls resulting in 11% survival. Treatments of 2.5, 5 and 10mgL(-1) PAA were significantly different from the controls (P<0.05). The highest percent survival of hatched fry was with 5mgL(-1) PAA administered twice daily; the 2.5mgL(-1) PAA treatment had slightly less survival, but gives a higher margin of safety in case of treatment error. Very little fungus was present in treatments receiving 2.5mgL(-1) PAA or higher, and concentrations of 15 and 20mgL(-1) PAA were toxic to the eggs. The mean survivals in the 0, 2.5, 5, 10, 15 and 20mgL(-1) PAA treatments were 11%, 60%, 63%, 62%, 32% and 0%, respectively. Therefore, PAA may be a compound that merits further investigations regarding its use in U.S. aquaculture.

Chemotherapy only for localized Hodgkin lymphoma.

Radiation therapy (RT) alone and more recently in combination with chemotherapy (combined modality therapy; CMT) has been the cornerstone of curative treatment for early-stage Hodgkin lymphoma (HL) for over 40 years. Because of increasing awareness of the late morbidity and mortality associated with RT, recent treatment regimens have attempted to limit its use. Chemotherapy only has been demonstrated to be a treatment option for most patients with localized HL. Current clinical trials have targeted subgroups of such patients who may be at an increased risk of recurrence for the addition of limited RT to chemotherapy.

The tyrosine kinase p56lck is essential in coxsackievirus B3-mediated heart disease.

Infections are thought to be important in the pathogenesis of many heart diseases. Coxsackievirus B3 (CVB3) has been linked to chronic dilated cardiomyopathy, a common cause of progressive heart disease, heart failure and sudden death. We show here that the sarcoma (Src) family kinase Lck (p56lck) is required for efficient CVB3 replication in T-cell lines and for viral replication and persistence in vivo. Whereas infection of wild-type mice with human pathogenic CVB3 caused acute and very severe myocarditis, meningitis, hepatitis, pancreatitis and dilated cardiomyopathy, mice lacking the p56lck gene were completely protected from CVB3-induced acute pathogenicity and chronic heart disease. These data identify a previously unknown function of Src family kinases and indicate that p56lck is the essential host factor that controls the replication and pathogenicity of CVB3.

The CD3 chains of the T cell antigen receptor associate with the ZAP-70 tyrosine kinase and are tyrosine phosphorylated after receptor stimulation.

Recent work indicates that signaling events resulting from stimulation of the T cell antigen receptor (TCR) can be initiated by the CD3 complex (gamma, delta, epsilon) as well as the zeta chains of the receptor. To help characterize the signaling function of CD3 we examined its associated tyrosine kinase activity since induction of tyrosine phosphorylation is one of the earliest signaling events. Our results indicate that at least two kinases, lck and ZAP-70, contribute to the CD3-associated kinase activity. A likely target of this activity is the CD3 complex itself since we observed that TCR stimulation resulted in rapid tyrosine phosphorylation of the CD3 epsilon and delta chains. To examine the function of the CD3 epsilon chain in particular, we constructed a chimera that fused the extracellular and transmembrane domains of CD8 to the cytoplasmic domain of CD3 epsilon. This chimera demonstrated that CD3 epsilon was independently capable of associating with proteins having tyrosine kinase activity, including ZAP-70. Our results show that the kinase activity that associates with the CD3 complex has characteristics that are quite similar to the previously characterized zeta-associated kinase activity. This finding suggests that both these components of the TCR initiate signaling events using a common mechanism. However, differences in their signaling function could result from recognition of distinct substrates.

Proline residues in CD28 and the Src homology (SH)3 domain of Lck are required for T cell costimulation.

The Src family tyrosine kinases Lck and Fyn are critical for signaling via the T cell receptor. However, the exact mechanism of their activation is unknown. Recent crystal structures of Src kinases suggest that an important mechanism of kinase activation is via engagement of the Src homology (SH)3 domain by proline-containing sequences. To test this hypothesis, we identified several T cell membrane proteins that contain potential SH3 ligands. Here we demonstrate that Lck and Fyn can be activated by proline motifs in the CD28 and CD2 proteins, respectively. Supporting a role for Lck in CD28 signaling, we demonstrate that CD28 signaling in both transformed and primary T cells requires Lck as well as proline residues in CD28. These data suggest that Lck plays an essential role in CD28 costimulation.

Stanford V program for locally extensive and advanced Hodgkin lymphoma: the Memorial Sloan-Kettering Cancer Center experience.

BACKGROUND: The Stanford group has reported excellent results with the Stanford V regimen for patients with bulky and/or advanced Hodgkin lymphoma (HL). However, Gobbi reported markedly inferior failure-free survival (FFS) comparing Stanford V to other regimens but included major deviations from the original program. We retrospectively examined whether treatment at our institution carefully following Stanford V guidelines would confirm the original Stanford outcome data. PATIENTS AND METHODS: From June 1995 to May 2002, 126 patients with either locally extensive or advanced HL were treated with the 12-week Stanford V chemotherapy program followed by 36-Gy involved-field radiotherapy to sites initially > or =5 cm and/or to macroscopic splenic disease. Overall, 26% had stage IV disease and 20% had international prognostic score (IPS) > or =4. Overall survival (OS), disease-specific survival, progression-free survival (PFS), FFS, and freedom from second relapse (FF2R) were determined. RESULTS: The 5- and 7-year OS were 90% and 88%, respectively. The 5-year FFS was 78%. IPS > or =4 was a significant independent predictor of worse OS and PFS. The FF2R was 64% at 3 years. CONCLUSION: Stanford V with appropriate radiotherapy is a highly effective regimen for locally extensive and advanced HL.

Determination of water quality variables, endotoxin concentration, and Enterobacteriaceae concentration and identification in southern High Plains dairy lagoons.

The objectives of this study were to determine the concentration of endotoxin, determine 20 water quality variables, and identify and enumerate fungal and bacterial pathogens from United States southern High Plains dairy lagoons and control lakes during summer and winter. Water samples were collected in triplicate from the north, south, east, and west quadrants of each body of water. The mean (+/- SEM) winter dairy lagoon endotoxin concentration was significantly higher (9,678+/-1,834 ng/mL) than the summer concentration (3,220+/-810 ng/mL). The mean endotoxin concentration of the 2 control lakes (summer: 58.1+/-8.8 ng/mL; winter: 38.6+/-4.2 ng/mL) was significantly less than that of the dairy lagoons. Two hundred-one Salmonella enterica spp. isolates were identified, 7 serovars were recovered from the dairy lagoons, and 259 Salmonella ssp. were identified from 5 other dairy locations (milk barn, ditch effluent, settling basin, feed alley pad flush, and center pivots). Twenty-eight Salmonella spp. were identified from center pivot water. Escherichia coli O157:H7 pathogens were isolated from other dairy locations but not from lagoons. Neither Salmonella spp. nor E. coli O157:H7 were identified from control lakes. Enterobacteriaceae opportunistic pathogens were isolated from both dairies and control lakes. Important mesophilic and thermophilic catabolic (to manure biosolids) fungal isolates were identified from dairy effluent locations, but no thermophilic fungal isolates were cultured from the control lakes. Adequate curing of green forage following center pivot irrigation is important to kill lagoon water enteric pathogens, even though the lagoon water is mixed with fresh water. Recirculating lagoon water to flush the feed alley pad, where cows stand while eating, to remove manure and using lagoon water to abate dairy dust in loafing pens and unimproved dairy roads is inconsistent with good environmental practice management.

Growth control variant cell line having increased serum requirement and decreased response to platelet-derived growth factor: reversion by 5-azacytidine.

Variants of the mouse embryo fibroblast X melanoma hybrid clone 100A have been isolated by a procedure that selects against cells that are able to grow in medium containing low concentrations of serum plus insulin. Three variant clones derived from this selection were found to have a much higher serum requirement than the parental clone 100A cells, as evidenced by a very low rate of DNA synthesis and growth in medium containing low concentrations of serum. Two of the variants had approximately double the number of chromosomes as the parental cell line, while one had approximately the same number of chromosomes as the parental cells. One of the variants was very strongly reverted by 5-azacytidine but not by ethyl methanesulfonate, suggesting that it reverted by a nonmutational mechanism such as a stable change in DNA methylation. Analysis of the growth requirements in hormone-supplemented serum-free media of the 100A parent, the INS 471 variant, and revertants of the variant indicated that the variant had a specific deficiency in its growth response to platelet-derived growth factor (PDGF). PDGF dose-response curves obtained with the variant cells were shifted approximately an order of magnitude toward higher PDGF concentrations relative to PDGF dose-response curves obtained with the parental 100A cells. This quantitative increase in PDGF requirement of the INS 471 variant appears to explain the increased serum requirement of this variant. Equilibrium binding experiments performed with 125I-PDGF suggest that the variant does not have a decreased number of PDGF receptors.

Molecular basis of T cell inactivation by CTLA-4.

CTLA-4, a negative regulator of T cell function, was found to associate with the T cell receptor (TCR) complex zeta chain in primary T cells. The association of TCRzeta with CTLA-4, reconstituted in 293 transfectants, was enhanced by p56(lck)-induced tyrosine phosphorylation. Coexpression of the CTLA-4-associated tyrosine phosphatase, SHP-2, resulted in dephosphorylation of TCRzeta bound to CTLA-4 and abolished the p56(lck)-inducible TCRzeta-CTLA-4 interaction. Thus, CTLA-4 inhibits TCR signal transduction by binding to TCRzeta and inhibiting tyrosine phosphorylation after T cell activation. These findings have broad implications for the negative regulation of T cell function and T cell tolerance.

Evaluation of potassium permanganate against an experimental subacute infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus (Rafinesque).

An experiment was performed to evaluate the efficacy of potassium permanganate (KMnO4) as a prophylactic and therapeutic treatment of an experimental subacute infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus. Fish were cutaneously abraded and divided into five treatment groups: (i) challenged by waterborne exposure to F. columnare and not treated with KMnO4 (positive control), (ii) challenged and simultaneously treated with KMnO4, (iii) challenged and treated with KMnO4 at 1, 6 and 9 days post-challenge, (iv) not challenged and treated with KMnO4 at 1, 6 and 9 days post-challenge (first negative control) and (v) not challenged and not treated (second negative control). The dosing of KMnO4 was 2.0 mg L(-1) above the potassium permanganate demand for 2 h duration. The survival of the group challenged and simultaneously treated with KMnO4 (99%) was significantly higher than the positive control (78%) and was not significantly different from the negative control groups. The challenged fish treated with KMnO4 post-challenge had 7% higher survival than the positive control (85% compared with 78%), but that difference was not statistically significant. The results demonstrate that KMnO4 has a clear prophylactic value but probably a marginal therapeutic value once the infection has established.

Ambient and indoor particulate aerosols generated by dairies in the southern High Plains.

The objectives were to quantify and size ambient aerosolized dust in and around the facilities of 4 southern High Plains dairies of New Mexico and to determine where health of workers might be vulnerable to particulate aerosols, based on aerosol concentrations that exceed national air quality standards. Ambient dust air samples were collected upwind (background) and downwind of 3 dairy location sites (loafing pen boundary, commodity, and compost field). The indoor milking parlor, a fourth site, was monitored immediately upwind and downwind. Aerosolized particulate samples were collected using high-volume sequential reference air samplers, laser aerosol monitors, and cyclone air samplers. The overall (main effects and estimable interactions) statistical general linear model statement for particulate matter (PM(10); particulate matter with an aerodynamic diameter of up to 10 microm) and PM(2.5) resulted in a greater mean concentration of dust in the winter (PM(10) = 97.4 +/- 4.4 microg/m(3); PM(2.5) = 32.6 +/- 2.6 microg/m(3)) compared with the summer (PM(10) = 71.9 +/- 5.0 microg/m(3); PM(2.5) = 18.1 +/- 1.2 microg/m(3)). The upwind and downwind boundary PM(10) concentrations were significantly higher in the winter (upwind = 64.3 +/- 9.5 microg/m(3); downwind = 119.8 +/- 13.0 microg/m(3)) compared with the summer (upwind = 35.2 +/- 7.5 microg/m(3); downwind = 66.8 +/- 11.8 microg/m(3)). The milking parlor PM(10) and PM(2.5) concentration data were significantly higher in the winter (PM(10) = 119.5 +/- 5.8 microg/m(3); PM(2.5) = 55.3 +/- 5.8microg/m(3)) compared with the summer (PM(10) = 88.6.0 +/- 5.8 microg/m(3); PM(2.5) = 21.0 +/- 2.1 microg/m(3)). Personnel should be protected from high aerosol concentrations found at the commodity barn, compost field, and milking parlor during the winter.

Growth-stimulatory actions of insulin in vitro and in vivo.

Insulin stimulates the growth and proliferation of a variety of somatic cells in culture, and evidence suggests that insulin is also an important regulator of growth in vivo. In cell culture, insulin interacts synergistically with other hormones and growth factors such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), tumor-promoting phorbol esters, and thrombin, to stimulate progression through the cell cycle of cells that have been arrested in G1 by deprivation for serum. In addition, insulin is required by most cells for optimal long term growth in hormone-supplemented serum-free media. In some cells, such as human skin fibroblasts, the growth-promoting effects of insulin appear to be mediated primarily by its low affinity interaction with receptors for insulin-like growth factor I (IGF-I). In other cells, such as hepatocytes, hepatoma cells, adrenocortical tumor cells, mammary carcinoma cells, and F9 embryonal carcinoma cells, insulin appears to stimulate growth by binding to high affinity insulin receptors. The insulin and IGF-I receptor proteins, like the receptor proteins for other growth-promoting hormones such as EGF and PDGF, are closely associated with tyrosine-specific protein kinase activities. The mechanism by which the binding of insulin to its receptor and activation of the receptor-associated tyrosine protein kinase activity control intracellular protein phosphorylation and dephosphorylation reactions, such as the phosphorylation of ribosomal protein S6, is a subject of considerable current interest. The phosphorylation of ribosomal protein S6 may be related mechanistically to the activation by insulin of protein synthesis, and hence the passage of cells through the G1 phase of the cell cycle. Malignant transformation does not generally result in a total loss of the growth requirement of cells for insulin or insulin-like growth factors, although transformation is accompanied in some cases by a qualitative reduction in the insulin/IGF requirement. Abnormalities in insulin production or sensitivity in vivo are accompanied by abnormalities in growth; thus, insulin appears to be an important regulator of growth in vivo. Some of the growth-promoting effects of insulin in vivo may be attributable to direct action of insulin, while other effects may be caused by the regulatory effect of insulin on somatomedin production, and possibly on somatomedin action.

Role of salivary protease activity in adherence of gram-negative bacilli to mammalian buccal epithelial cells in vivo.

Serious illness is accompanied by markedly increased susceptibility to colonization of the respiratory tract by gram-negative bacilli and an increase in the number of such organisms which adhere to regional epithelial cells during incubation in vitro. Trypsinization of cells from normal subjects causes a similar increase in bacillary adherence. We studied bacillary adherence to buccal cells in vitro, protease activity of upper respiratory secretions with a fibrin plate technique, and the amount of fibronectin on the surface of buccal cells with a direct radioimmunobinding assay. Among 10 patients seriously ill with acute respiratory failure bacillary adherence to buccal cells and protease activity in secretions were increased compared with controls and cell-surface fibronectin was decreased; all patients were colonized in vivo with gram-negative bacilli. These changes were persistent and 80% of the patients died. Serial determinations were made in eight patients undergoing coronary artery bypass surgery. Following surgery, protease activity and bacillary adherence increased and cell-surface fibronectin decreased; 38% of coronary artery bypass patients became colonized. In these uncomplicated patients the changes observed were transient, largely returning to normal by the third postoperative day. Increased protease activity of secretions and alterations in epithelial cell surfaces as reflected by loss of buccal cell-surface fibronectin occur swiftly after major illness and appear to underlie enhanced cell adherence of bacilli and colonization of the upper respiratory tract. These findings suggest new approaches to the prevention of nosocomial pneumonia.

Dexamethasone protection of rat intestinal epithelial cells against oxidant injury is mediated by induction of heat shock protein 72.

Although the therapeutic actions of glucocorticoids are largely attributed to their anti-inflammatory and immunosuppressive effects, they have been implicated in enhancing tissue and cellular protection. In this study, we demonstrate that dexamethasone significantly enhances viability of IEC-18 rat small intestinal cells against oxidant-induced stress in a dose-dependent fashion. This protective action is mediated by induction of hsp72, the major inducible heat shock protein in intestinal epithelial cells. Dexamethasone stimulates a time- and dose-dependent response in hsp72 protein expression that parallels its effects on cell viability. Furthermore, the induction of hsp72 is tissue dependent, as nonintestinal epithelioid HeLa cells show differential induction of hsp72 expression in response to the same dexamethasone treatment. Antisense hsp72 cDNA transfection of IEC-18 cells abolishes the dexamethasone-induced hsp72 response, without significantly affecting constitutive expression of its homologue, hsc73. Dexamethasone treatment also significantly induces hsp72 protein expression in rat intestinal mucosal cells in vivo. These data demonstrate that glucocorticoids protect intestinal epithelial cells against oxidant-induced stress by inducing hsp72.

Maintaining the dose intensity of ICE chemotherapy with a thrombopoietic agent, PEG-rHuMGDF, may confer a survival advantage in relapsed and refractory aggressive non-Hodgkin lymphoma.

INTRODUCTION: HDT/ASCT is standard for relapsed and refractory DLCL patients responding to second-line chemotherapy. We incorporated a thrombopoietic agent into the ICE chemotherapy program to potentially: decrease platelet associated toxicities, augment stem cell collection and maintain dose intensity. METHODS: This randomized, double-blind, placebo-controlled phase I/II trial examines PEG-rHuMGDF versus placebo with ICE chemotherapy. Phase I compared three cohorts and defined a clinically effective dose (CED). Phase II evaluated the CED versus placebo. Outcome measures included safety, hematological end-points, stem cell collection and the impact of dose-intensity on outcome. RESULTS: Forty-one patients with primary refractory (16) or relapsed DLCL (25) were treated; Response rates for evaluable patients are: 75% (12/16) for placebo and 82% (18/22) for PEG-rHuMGDF. PEG-rHuMGDF treated patients had significantly less grade IV thrombocytopenia, higher median platelet nadirs, and less platelet transfusion per cycle. ICE dose intensity was improved with PEG-rHuMGDF versus placebo: 75 versus 42% (P = 0.008). At 8.5 years median follow-up, overall and event-free survival are 47 and 31%, respectively. Patients treated on PEG-rHuMGDF versus placebo had improved survival (59 versus 31%, P = 0.06). CONCLUSION: PEG-rHuMGDF ameliorated thrombocytopenia, improved platelet recovery, and maintained ICE dose intensity. Potential survival advantages conferred by maintaining dose intensity require validation with newer thrombopoietic agents.

Genetic engineering in the Precambrian: structure of the chicken triosephosphate isomerase gene.

We report the sequence of the single chicken triosephosphate isomerase gene and its flanking regions. The 3-kilobase-long gene is composed of seven similarly sized exons and six introns. By using crystallographic and sequence data, we argue that this ancient gene was originally assembled from the genetic antecedents of exons.

Genetic evidence of a role for Lck in T-cell receptor function independent or downstream of ZAP-70/Syk protein tyrosine kinases.

T-cell antigen receptor (TCR) engagement results in sequential activation of the Src protein tyrosine kinases (PTKs) Lck and Fyn and the Syk PTKs, ZAP-70 and Syk. While the Src PTKs mediate the phosphorylation of TCR-associated signaling subunits and the phosphorylation and activation of the Syk PTKs, the lack of a constitutively active Syk PTK has prohibited the analysis of Lck function downstream of these initiating signaling events. We describe here the generation of an activated Syk family PTK by substituting the kinase domain of Syk for the homologous region in ZAP-70 (designated as KS for kinase swap). Expression of the KS chimera resulted in its autophosphorylation, the phosphorylation of cellular proteins, the upregulation of T-cell activation markers, and the induction of interleukin-2 gene synthesis in a TCR-independent fashion. The KS chimera and downstream ZAP-70 or Syk substrates, such as SLP-76, were still phosphorylated when expressed in Lck-deficient JCaM1.6 T cells. However, expression of the KS chimera in JCaM1.6 cells failed to rescue downstream signaling events, demonstrating a functional role for Lck beyond the activation of the ZAP-70 and Syk PTKs. These results indicate that downstream TCR signaling pathways may be differentially regulated by ZAP-70 and Lck PTKs and provide a mechanism by which effector functions may be selectively activated in response to TCR stimulation.

Differential T-cell antigen receptor signaling mediated by the Src family kinases Lck and Fyn.

Src family tyrosine kinases play a key role in T-cell antigen receptor (TCR) signaling. They are responsible for the initial tyrosine phosphorylation of the receptor, leading to the recruitment of the ZAP-70 tyrosine kinase, as well as the subsequent phosphorylation and activation of ZAP-70. Molecular and genetic evidence indicates that both the Fyn and Lck members of the Src family can participate in TCR signal transduction; however, it is unclear to what extent they utilize the same signal transduction pathways and activate the same downstream events. We have addressed this issue by examining the ability of Fyn to mediate TCR signal transduction in an Lck-deficient T-cell line (JCaM1). Fyn was able to induce tyrosine phosphorylation of the TCR and recruitment of the ZAP-70 kinase, but the pattern of TCR phosphorylation was altered and activation of ZAP-70 was defective. Despite this, the SLP-76 adapter protein was inducibly tyrosine phosphorylated, and both the Ras-mitogen-activated protein kinase and the phosphatidylinositol 4, 5-biphosphate signaling pathways were activated. TCR stimulation of JCaM1/Fyn cells induced the expression of the CD69 activation marker and inhibited cell growth, but NFAT activation and the production of interleukin-2 were markedly reduced. These results indicate that Fyn mediates an alternative form of TCR signaling which is independent of ZAP-70 activation and generates a distinct cellular phenotype. Furthermore, these findings imply that the outcome of TCR signal transduction may be determined by which Src family kinase is used to initiate signaling.