Ellis L. Reinherz

The differentiation and function of human T lymphocytes

of Tumor Immunology Sidney Farber Cancer Institute and Department of Medicine Harvard Medical School Boston, Massachusetts 0211.5 The precise dissection of cellular mechanisms and interactions involved in the generation of human T cell responses has been facilitated in recent years by advances in four areas: first, the development of in

An alternative pathway of T-cell activation: A functional role for the 50 kd T11 sheep erythrocyte receptor protein

A series of seven monoclonal antibodies was produced against the T-lineage-specific 50 kd T11 sheep erythrocyte rosette (SRBC) receptor protein in order to define the function of the molecule. Three distinct epitopes were detected: T11(1), the SRBC binding site expressed on all T lymphocytes and thymocytes; T11(2), an epitope unrelated to the SRBC binding site but with a similar distribution; and T11(3), a neo-epitope expressed only upon T-cell activation. Simultaneous triggering of T11(2) and T11(3) epitopes by monoclonal antibodies induces T lymphocytes to proliferate and mediate their functional programs in the absence of antigen and/or antigen-presenting cells. This antigen-independent mode of triggering is distinct from that involving the T3-Ti antigen receptor complex and represents an alternate pathway of T-cell activation. Given that T11 is the earliest T-lineage surface glycoprotein to appear in thymic ontogeny and is thus expressed before T3-Ti, the former may be involved in clonal expansion and/or differentiation during early development.

Current concepts in immunology: Regulation of the immune response--inducer and suppressor T-lymphocyte subsets in human beings.

HUMAN T lymphocytes are endowed with the capacity to recognize specific antigens, execute effector functions, and regulate the type and intensity of virtually all cellular and humoral immune respon...

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.

Loss of suppressor T cells in active multiple sclerosis. Analysis with monoclonal antibodies.

To determine whether abnormalities of immunoregulatory T cells are associated with multiple sclerosis (MS), we characterized peripheral lymphocytes in 33 patients with untreated MS and compared them with 42 normal persons and 29 age-matched control subjects who had other neurologic diseases. For this analysis, we used monoclonal antibodies to the surface antigens of helper (T4) and suppressor (T5) T-cell subsets and to a common T-cell antigen (T3). In contract to normal persons and the controls with other neurologic diseases, the patients with MS had a reduced percentage of T3-positive (T3+) cells (P less than 0.05). More importantly, there was a selective decrease in T5-positive (T5+) cells in 11 of 15 patients with active MS, but in only one of 18 patients with inactive MS and in none of the normal persons or controls with neurologic disease (P less than 0.00001). Serial analysis of five patients with MS showed a correlation between the absence of the T5+ subset and disease activity. Thus, there is loss of peripheral suppressor cells in many patients with active MS, suggesting that immunoregulatory abnormalities contribute to the pathogenesis of the disease.

Analysis of host-virus interactions in AIDS with anti-gp120 T cell clones: Effect of HIV sequence variation and a mechanism for CD4+ cell depletion

The primary human T cell response to HIV was analyzed by isolating from seronegative donors T cell clones specific for HIV gp120. T cell epitopes restricted by different MHC elements were identified within gp120, and synthetic peptides were used to address the fundamental problem of how HIV sequence variability affects T cell recognition. Even one conservative substitution can drastically reduce recognition; thus the interaction of gp120 epitopes with T cell receptors and MHC is precise and poorly crossreactive. Importantly, a subset of CD4+ gp120-specific clones manifest cytolytic activity and lyse uninfected autologous CD4+Ia+ T cells in the presence of gp120 in a process that is strictly dependent upon CD4-mediated uptake of gp120 by T cells. Assuming gp120 is shed from HIV-infected cells in vivo, this novel CD4-dependent autocytolytic mechanism may contribute to the profound depletion of CD4+ cells in AIDS.

Multiple sclerosis: Distribution of T cells, T cell subsets and Ia-positive macrophages in lesions of different ages

Using monoclonal antibodies in combination with the PAP technique, total (T11+) T cells, helper-inducer (T4+) T cells, suppressor-cytotoxic (T8+) T cells and Ia+ cells (macrophages and B cells) were localized in frozen sections of multiple sclerosis (MS) lesions with varied disease activity. In acute MS, T11+, T4+, T8+ cells and Ia+ macrophages were found in large numbers throughout the lesion but were virtually absent from normal white matter. In active chronic MS lesions, the numbers of T11+, T4+ and T8+ cells increased from the center towards the edge of the lesion. T11+ and T4+ cells penetrated deeply into the normal-appearing white matter adjacent to the lesion, while T8+ cells were more confined to the lesion edge. Ia+ macrophages displayed a reverse distribution pattern to that of T cells. They showed the highest density in the lesion center and their numbers decreased slightly towards the lesion edge. Small numbers of T11+, T4+, T8+ and Ia+ cells were always present in normal white matter. In silent chronic MS lesions, the numbers of both T cells and Ia+ cells were significantly lower than in active chronic MS. While T11+ and T4+ cells were found throughout the central nervous system (CNS), T8+ cells were virtually absent from the lesion center. Ia+ macrophages were also present in small numbers throughout the CNS and, sometimes, showed some accumulation at the lesion edge. Thus, T cells and T cell subsets have been demonstrated to be involved in lesion pathogenesis in MS in that lesion progression was associated with T4+ cells while ongoing demyelination depended upon the presence of Ia+ macrophages.

In Vivo Activated T Lymphocytes in the Peripheral Blood and Cerebrospinal Fluid of Patients with Multiple Sclerosis

We found an increase in peripheral-blood lymphocytes bearing the T-cell-specific activation antigen Ta1 in 20 of 35 patients with progressive multiple sclerosis, 4 of 18 patients with stable or improving multiple sclerosis, 1 of 17 patients with other neurologic diseases, and 1 of 14 normal controls (P less than 0.0002, Fishers exact test). No increases in two other markers of T-cell activation, T113 and the interleukin-2 receptor, were found. In the cerebrospinal fluid, patients with progressive multiple sclerosis (pleocytosis, 3.9 +/- 1.6 cells per cubic millimeter) had 42 +/- 3.0 per cent Ta1+ cells. In contrast, patients with other inflammatory central nervous system diseases (36 +/- 13 cells per cubic millimeter) had 9.6 +/- 1.8 per cent Ta1+ cells (P less than 0.01). In patients with other neurologic diseases without inflammation (0.7 +/- 0.16 cells per cubic millimeter), the percentage of Ta1+ cells was equivalent to that in patients with multiple sclerosis (39 +/- 5.4 per cent), although the absolute number was lower. There was a positive correlation between the presence of Ta1+ cells in the spinal fluid and blood of patients with other neurologic diseases, but not patients with multiple sclerosis. Less than 1 per cent of lymphocytes from the spinal fluid of patients with multiple sclerosis expressed interleukin-2 receptors, as compared with 9.8 per cent of cells from subjects with other inflammatory neurologic diseases (P less than 0.01). These results suggest that the T cells in the spinal fluid of patients with multiple sclerosis may be activated by a different mechanism or in a different temporal sequence from that in patients with other nervous system diseases. Furthermore, the increase in Ta1+ cells in the peripheral blood of patients with multiple sclerosis demonstrates systemic immune activation in the disease; monitoring such cells may provide an objective measure of abnormal immunologic activity.

Sequence variability analysis of human class I and class II MHC molecules: Functional and structural correlates of amino acid polymorphisms

Major histocompatibility complex class I (MHCI) and class II (MHCII) molecules display peptides on antigen-presenting cell surfaces for subsequent T-cell recognition. Within the human population, allelic variation among the classical MHCI and II gene products is the basis for differential peptide binding, thymic repertoire bias and allograft rejection. While available 3D structural analysis suggests that polymorphisms are found primarily within the peptide-binding site, a broader informatic approach pinpointing functional polymorphisms relevant for immune recognition is currently lacking. To this end, we have now analyzed known human class I (774) and class II (485) alleles at each amino acid position using a variability metric (V). Polymorphisms (V>1) have been identified in residues that contact the peptide and/or T-cell receptor (TCR). Using sequence logos to investigate TCR contact sites on HLA molecules, we have identified conserved MHCI residues distinct from those of conserved MHCII residues. In addition, specific class II (HLA-DP, -DQ, -DR) and class I (HLA-A, -B, -C) contacts for TCR binding are revealed. We discuss these findings in the context of TCR restriction and alloreactivity.

Conformation and function of the N-linked glycan in the adhesion domain of human CD2.

The adhesion domain of human CD2 bears a single N-linked carbohydrate. The solution structure of a fragment of CD2 containing the covalently bound high-mannose N-glycan [-(N-acetylglucosamine)2-(mannose)5-8] was solved by nuclear magnetic resonance. The stem and two of three branches of the carbohydrate structure are well defined and the mobility of proximal glycan residues is restricted. Mutagenesis of all residues in the vicinity of the glycan suggests that the glycan is not a component of the CD2-CD58 interface; rather, the carbohydrate stabilizes the protein fold by counterbalancing an unfavorable clustering of five positive charges centered about lysine-61 of CD2.