Herbert Levine

Antigen recognition by human T lymphocytes is linked to surface expression of the T3 molecular complex

Four distinct surface molecules on human T cells are defined by the monoclonal antibodies anti-T1, anti-T3 (anti-T3A), anti-T11 and anti-T12. Following cell binding, anti-T3 (anti-T3A) and anti-T1 induce independent modulation of their respective ligands, whereas anti-T11 and anti-T12 do not. To explore the biological consequences of this modulation, we used cloned populations of T4 and T8 cytotoxic T lymphocytes. Anti-T3 (anti-T3A), but not anti-T1, inhibits cytotoxic T lymphocyte effector function by T4 and T8 clones as well as antigen-specific T cell recognition. The latter is not secondary to a generalized inhibitory effect since responsiveness to interleukin 2 is maintained. Moreover, after modulation, cytotoxic T lymphocytes recover cytolytic function in parallel with reexpression of surface T3 molecules. We provide evidence for a direct linkage between antigen recognition by T lymphocytes and surface expression of the T3 molecular complex.

Role of the CD40 and CD95 (APO-1/Fas) antigens in the apoptosis of human B-cell malignancies

Ligation of CD40 inhibits apoptosis and stimulates proliferation of normal B cells, whereas ligation of CD95 (APO‐1/Fas) induces apoptosis of activated lymphocytes. Aberrant signalling through the CD40 and CD95 antigens could thus participate in the pathogenesis of lymphoid malignancies. The expression and function of CD40 and CD95 on neoplastic B cells from patients with acute lymphoblastic leukaemia (ALL), chronic lymphocytic leukaemia (CLL) and non‐Hodgkin’s lymphoma (NHL) were examined. CD40 was expressed by all 30 B‐cell tumours, whereas CD95 was detected on neoplastic B cells in only one of 10 cases of ALL, two of 10 cases of CLL, and three of 10 cases of NHL. Incubation with an agonistic CD95 monoclonal antibody (MoAb) did not augment apoptosis in any of the unstimulated B‐cell neoplasms. CD40 triggering did not consistently inhibit spontaneous apoptosis, but ultimately stimulated the growth of neoplastic B cells in most cases. Furthermore, CD40 activation led to up‐regulation of the CD95 antigen in all 30 B‐cell neoplasms. Ligation of CD95 on CD40‐activated tumour cells augmented apoptosis in five of 10 ALL, three of 10 CLL, and nine of 10 NHL cases. The degree of apoptosis induced by CD95 triggering was greater for NHL cells than for ALL cells or CLL cells. Bcl‐2 expression by ALL and NHL cells was substantially decreased after in vitro culture, whereas Bcl‐2 expression by CLL cells was not significantly changed. However, there was no correlation between the level of Bcl‐2 expression and sensitivity to CD95‐mediated apoptosis. Thus, factors other than levels of CD95 and Bcl‐2 determine susceptibility of malignant B cells to apoptosis after CD95 triggering. CD40‐activated lymphoma cells appear to be very sensitive to CD95‐mediated apoptosis, suggesting potential strategies for treatment of NHL. Elucidation of the mechanisms underlying resistance of ALL and CLL cells to CD95 triggering may facilitate the development of novel therapeutic approaches to these diseases as well.

Functional Consequences of APO-1/Fas (CD95) Antigen Expression by Normal and Neoplastic Hematopoietic Cells

Murine monoclonal antibody (mAb) 7C11 binds to the same cell surface epitope as anti-APO-1 and anti-Fas and reacts specifically with cells transfected with a cDNA encoding the human Fas antigen. Furthermore, incubation with 7C11 causes death of hematopoietic cell lines that express APO-1/Fas but not APO-1/Fas-negative cell lines. 7C11 therefore recognizes the human APO-1/Fas (CD95) antigen, a 40 to 50 kDa cell surface glycoprotein that can trigger apoptosis or programmed cell death. Expression of APO-1/Fas antigen by normal and neoplastic hematopoietic cells was determined by flow cytometry using 7C11. APO-1/Fas is expressed by approximately 30 to 40% of resting peripheral blood T cells, B cells, and monocytes and by approximately 5% of resting NK cells and thymocytes. It was not detected on granulocytes, erythrocytes, or platelets. Approximately 80 to 90% of activated T cells, B cells, and thymocytes express APO-1/Fas, as do the majority of activated NK cells. Perturbation of APO-1/Fas by 7C11 does not affect the viability of resting lymphocytes or monocytes. In contrast, activated T cells and NK cells undergo apoptosis within 3 hours of exposure to 7C11. Other mAb that stimulate T cells or NK cells do not cause rapid induction of programmed cell death. APO-1/Fas antigen is expressed by many cell lines of lymphoid and myeloid lineage. However, this antigen was detected on neoplastic cells from only one of 69 patients with acute myeloid leukemia, acute lymphoblastic leukemia, chronic myelogenous leukemia, chronic lymphocytic leukemia, or multiple myeloma. Only 3 out of 25 tumor samples from patients with non-Hodgkins lymphoma were found to express APO-1/Fas. All three of these lymphomas harbored the bcl-2-Ig fusion gene associated with the chromosomal translocation t (14;18). Conversely, only 27% of lymphomas that possessed the bcl-2-Ig gene were found to express the APO-1/Fas antigen. Like normal activated lymphocytes, leukemia and lymphoma cells that expressed APO-1/Fas antigen were found to undergo apoptosis in vitro after incubation with 7C11. The APO-1/Fas antigen appears to regulate the growth of normal hematopoietic cells, and the marked upregulation of this antigen on activated normal lymphocytes contrasts sharply with the absence of APO-1/Fas on neoplastic cells of hematopoietic lineage. Defects in the apoptotic signal delivered through this antigen might contribute to the pathogenesis of hematopoietic neoplasms. Thus, the gene encoding APO-1/Fas can be considered a novel type of tumor suppressor gene, just as bcl-2 can be considered a cellular proto-oncogene.

CD11 molecule defines two types of suppressor cells within the T8+ population

It has been shown that T8+ cells are comprised of functionally heterogeneous subpopulations such as suppressor, cytotoxic, and NK cells. In this report, we attempted to delineate the functional heterogeneity of T8 cells defined by anti-CD11 antibody (anti-Mol). Although allospecific cytotoxic activity was restricted to the T8+Mol- subset, suppression of PWM IgG synthesis could be elicited in both the T8+Mol+ and the T8+Mol- subset of cells. However, the mechanism of suppression was different in these two subsets. Suppression by the T8+Mol- subset of cells required the interaction with the T4+2H4+ suppressor inducer cells, whereas the T8+Mol+ subset of cells could suppress in the absence of the suppressor inducer cells. Moreover, recombinant interleukin-2 alone could augment this suppression by the T8+Mol+ subset, but did not induce suppression by the T8+Mol- subset. In contrast, NK and LAK activity was exclusively found in the T8+Mol+ subset of cells but not in the T8+Mol- subset of cells. These results suggest that the CD11 molecule is useful for distinguishing novel subsets of T8 cells.

Regulation of the 28 kDa heat shock protein by retinoic acid during differentiation of human leukemic HL-60 cells

Dysregulation of hematopoietic cellular differentiation contributes to leukemogenesis. Unfortunately, relatively little is known about how cell differentiation is regulated. Considering that heat shock proteins (hsp) and specifically the small hsps have been increasingly linked to growth regulation, we sought to determine whether the mammalian small hsp (hsp28) is a growth‐regulatory candidate during hematopoietic cell differentiation. Because of its effects on cell growth and differentiation and its increasing clinical use as a differentiating agent, we examined the effect of retinoic acid (RA) on hsp28 during differentiation of the human leukemic HL‐60 cell line. Although hsp28 was constitutively expressed at low levels in untreated HL‐60 cells, steady state hsp28 protein increased transiently, concomitant with the onset of G1 cell cycle arrest. Furthermore, hsp28 phosphorylation transiently increased within one hour following treatment with RA. Interestingly, in contrast to other differentiating agents the induction of hsp28 by RA was post‐transcriptionally mediated with hsp28 protein and mRNA being discordantly regulated. These observations underscore the complex regulation of hsp28 by RA during granulocytic differentiation of human leukemic cells and indicate hsp28 as an intermediary in the pathway through which retinoids exert their growth and differentiative effects.

Dynamics of SU(2) Lattice Gauge Theories

Abstract We study the dynamics of SU(2) lattice gaugee theories by concentrating on the underlying Z 2 structures of monopoles and vortices, adding a chemical potential for monopoles. The resulting abelian nature of these objects allows us to reliable computations for a wide range of couplings. In particular, by integrating over the non-abelian SO(3) degrees of freedom at strong coupling, an effective Z 2 theory emerges which at leading order is just the dual version of the Z 2 -Higgs model. The phase boundaries are predicted to a few percent, as verified by Monte Carlo simulations. Our approach provides a framework for explaining and comparing many of the recently discovered features of the theory, including the Creutz crossover and the SO(3) phase transition. Also, we speculate on the relevance of these ideas for confinement and precocious scaling.

Large N classical equations and their quantum significance

Abstract We show that the large N limits of a wide variety of vector models may be obtained by studying the classical equations of motion. In particular, we derive a constraint which allows us to choose solutions of the classical field equations which directly give the correlation functions of N → ∞ quantum system. Models studied here include quantum mechanics on a sphere, two-dimensional linear and nonlinear O(N) field theories and the CPN model.

Immune response gene control of antibody specificity

Abstract The expression of the histocompatibility-linked PLL Ir gene was investigated in guinea pig B cells. Strain 2 and F 1 (2 × 13) guinea pigs, immunized with the αDnp-Lys 9 , produce both T cells and antibody which are equally discriminatory for αDnp-Lys 9 . In contrast strain 13 (PLL Ir gene negative) guinea pigs immunized with αDnp-Lys 9 do not develop specific T-cell responses and the antibody produced while restricted in heterogeneity cannot differentiate the immunizing antigen from Dnp-OH. However, if in a F 1 (2 × 13) environment, PLL Ir gene-negative B cells are provided with F 1 (2 × 13) T cells they express the ability to make antibody as specific and discriminatory as the antibody produced by PLL Ir gene-positive B cells. These findings strongly suggest that in the guinea pigs the PLL Ir gene defect is localized to the T cells and that the repertoire of specificity of B cells is similar if not identical in both responder and nonresponder animals. In addition these observations support the notion that the cellular locus for the PLL Ir gene expression in the guinea pigs is limited to T cells and not to macrophages and B lymphocytes.

Pattern Formation Far from Equilibrium : The Free Space Dendritic Crystal

The selection of shape and velocity for the dendritic crystal has been an outstanding problem for several decades. Work over the past few years has revealed a new mechanism, that of “microscopic solvability” which resolves these issues. The mechanism relies on a non-perturbative contribution of the microscopic dynamics to create a consistency condition for the macroscopic pattern which in turn has a unique solution. This talk will focus on explaining the problem and its solution and furthermore on the generality of our approach, which to-date has been shown to apply to a variety of interfacial pattern forming systems.

Human thymocyte maturation in vitro: A flow cytometric analysis☆☆☆

Using an in vitro culture system, light scatter analyses, and two-color flow cytometry, we provide evidence that the interleukin-2 (IL-2) and transferrin receptors can be induced within 48 hr on nonproliferating immature thymocytes. The thymocytes (greater than 35%) that expressed the transferrin and IL-2 receptors demonstrated nuclear activation as measured by log 90 degrees light scatter analysis. Increases in antigen-receptor-associated T3-antigen expression followed transferrin and IL-2-receptor induction and occurred on maximally activated T4+T8+ thymocytes on Day 3 of culture. Maximal T3 expression did not occur until Days 5-7 and paralleled loss of T4, T8 coexpression, suggesting an association between a mature T3-Ti antigen receptor complex and a mature T4, T8 phenotype.