Clonal activation of cytotoxic lymphocyte precursors by monoclonal anti-CD3 antibody: analysis of feeder cell requirements

Activation of cytotoxic lymphocyte precursors (CLP) by the mitogenic monoclonal anti-CD3 antibody OKT3 was studied under limiting dilution (LD) culture conditions. One out of 2-6 E-rosette-purified T cells gave rise to a cytotoxic T cell (CTL) clone when cultured in the presence of OKT3 (0.2-2 ng/ml), recombinant IL-2 (100 U/ml), and irradiated feeder cells. Clonal CLP activation was optimally supported by a combination of E-rosette-depleted non-T feeder cells with small numbers of T cells added back. Among the cell lines tested, Fc-receptor-bearing monocytic cell lines U937 and HL-60 were efficient feeder cells whereas T cell lines (Jurkat, Molt-4, Ke37) did not support clonal CLP activation. These data indicate that clonal activation of CLP and differentiation into cytotoxic effector cells under LD culture conditions are critically influenced by the type and number of feeder cells used.

Antigen-presenting T cells. II. Clonal responses of alloreactive and virus-specific self-restricted human cytotoxic T cell responses stimulated by T lymphoblasts

The capacity of various stimulator cell types to present alloantigens or viral antigens to resting human CD8+ cytotoxic lymphocyte precursors (CLP) was analyzed in a limiting dilution culture system. Cell sorter-separated T lymphoblasts of both CD4+ and CD8+ phenotypes but not resting T cells were found to efficiently stimulate the clonal development of allogeneic CD8+ CLP. Thus, 5000 CD4+ T lymphoblasts activated as many (one out of 200 to one out of 300) allogeneic CLP as 50,000 peripheral blood mononuclear stimulator cells. This potent stimulator activity was found in CD4+ and CD8+ T lymphoblasts activated by mitogen, anti-T3 monoclonal antibody, or mixed leukocyte reactions. Cytotoxic T cells generated in this system were highly specific for HLA class I antigens. Furthermore, T lymphoblasts infected with mumps virus efficiently induced development of autologous CLP into CTL clones that were virus specific and self-HLA restricted, as shown by split-well analysis. The possible in vivo significance of antigen-presenting T lymphoblasts is discussed.

Antigen-presenting T cells. II. Clonal responses of alloreactive and virus-specific self-restricted human cytotoxic T cell responses stimulated by T lymphoblasts

The capacity of various stimulator cell types to present alloantigens or viral antigens to resting human CD8+ cytotoxic lymphocyte precursors (CLP) was analyzed in a limiting dilution culture system. Cell sorter-separated T lymphoblasts of both CD4+ and CD8+ phenotypes but not resting T cells were found to efficiently stimulate the clonal development of allogeneic CD8+ CLP. Thus, 5000 CD4+ T lymphoblasts activated as many (one out of 200 to one out of 300) allogeneic CLP as 50,000 peripheral blood mononuclear stimulator cells. This potent stimulator activity was found in CD4+ and CD8+ T lymphoblasts activated by mitogen, anti-T3 monoclonal antibody, or mixed leukocyte reactions. Cytotoxic T cells generated in this system were highly specific for HLA class I antigens. Furthermore, T lymphoblasts infected with mumps virus efficiently induced development of autologous CLP into CTL clones that were virus specific and self-HLA restricted, as shown by split-well analysis. The possible in vivo significance of antigen-presenting T lymphoblasts is discussed.

Use of V beta.8 genes in splenic Lyt-2+ cytotoxic lymphocyte precursors reactive to bm1 or bm14 alloantigen in individual C57BL/6 mice

The cytotoxic response of cell sorter-purified small Lyt-2+ splenic cytotoxic lymphocyte precursors from 10 individual C57BL/6 mice to mutant class I H-2Kbm1 or H-2Dbm14 allodeterminants was analyzed under limiting dilution conditions. The cytotoxic activity of anti-bm1-specific or anti-bm14-specific cytotoxic T lymphocyte (CTL) populations (selected for a high probability of clonality) was tested against F23 hybridoma cells; F23+ CTL clones lysed F23 hybridoma targets but F23- CTL clones did not. In the C57BL/6 anti-bm1 mixed lymphocyte reaction, 36% (range 29-48%) of the generated CTL clones were F23+; in the B6-anti-bm14 mixed lymphocyte reaction, 45% (range 34-49%) of the generated CTL clones were F23+. Hence, a large fraction of the anti-bm1- or anti-bm14-reactive CTL clones from C57BL/6 mice use V beta.8 genes to construct these allospecific T cell receptor phenotypes, but no extensive variation in the use of V beta.8 genes in the construction of allospecific T cell receptor phenotypes of restricted heterogeneity is found in individual mice of the same strain.

Survival and revival times of the retina: ERG studies at total ocular ischemia in rabbits and cats

Retinal survival and revival times were measured in cats and rabbits at controlled retinal temperatures. While the great difference between b-wave survival times in cats and rabbits was confirmed, the revival times were distinctly shorter (30 min) than those previously found.

Introduction of a selectable gene into murine T-lymphoblasts by a retroviral vector

A recombinant retroviral vector with an inserted bacterial neomycin resistance (neo) gene was used to transfer in vitro neomycin resistance (neoR) into murine cytotoxic lymphocyte precursors (CLP). The infection protocol involved co-cultivation of mitogen-activated splenic T-blasts with irradiated cells that produced either the recombinant retrovirus plus a helper virus, or exclusively the recombinant retrovirus. Infected T-blasts were subsequently cultured under limiting dilution (LD) conditions that supported clonal in vitro development of a large fraction of murine CLP. In infected T-blast populations, frequency estimates were obtained for CLP that developed into functional cytotoxic T-lymphocyte (CTL) populations under G418-selected or non-selected conditions; from these frequency estimates, an efficiency of transduction of the neoR phenotype into murine CLP of 2-8% was calculated. Some conditions were defined that influenced transduction efficiency, i.e., the density of the infecting monolayer cells; the presence of interleukin 2-containing conditioned medium and mitogenic lectins during the co-culture period; a delayed onset of G418 selection after infection. It was demonstrated that the neoR phenotype of functional CTL populations derived from infected CLP resulted from expressed recombinant retrovirus.

Host-reactive cytotoxic T lymphocyte precursors in long-lived fully allogeneic mouse bone marrow chimeras

Fully H-2-incompatible chimeric mice were constructed by grafting lethally (950 rad) irradiated germ-free (GF) CBA (H2k) mice with anti-Thy 1 antibody plus complement-treated allogeneic C57Bl/6 (B6) (H2b) bone marrow cells. These chimeric mice were kept for more than 11 months, either under GF conditions or under barrier-sustained specific-pathogen-free (SPF) conditions. Controls included nonirradiated, nontransplanted, sex- and age-matched CBA and B6 mice raised under SPF conditions, and syngeneic chimeric mice of the CBA----CBA type kept under GF and SPF conditions. All chimeric mice were completely repopulated with donor-type lymphoid cells and showed no clinical or histological evidence of graft-versus-host disease. From the fully allogeneic chimeric mice, we enumerated the numbers of splenic cytotoxic T lymphocyte precursors (CTL-p) that could be clonally expanded under limiting dilution conditions in response to third-party alloantigens, or nonmodified and trinitrophenyl (TNP)-modified stimulator cells bearing host or donor H-2 antigens. The existence of high numbers of alloreactive and host- or donor-type H-2-restricted TNP-specific CTL-p in the spleens of fully allogeneic chimeras indicated almost normal immunocompetence. The surprising finding, however, was that large numbers of host (CBA)-reactive splenic CTL-p were inducible under limiting dilution conditions in healthy long-lived allogeneic chimeras, although these chimeric mice were devoid of any histological or clinical signs of graft-versus-host disease.

Allorestricted cytotoxic T cells. Large numbers of allo-H-2Kb-restricted antihapten and antiviral cytotoxic T cell populations clonally develop in vitro from murine splenic precursor T cells

Cytotoxic T lymphocyte (CTL) responses of splenic T cells from C57BL/6 B6) mice and mutant H-2Kbm1 (bm1) mice to haptenic (trinitrophenyl [TNP] ) and herpes simplex virus (HSV) determinants in the context of an allogenic (wild-type or mutant) H-2Kb molecule were analyzed in a modified limiting dilution system. In the B6-anti-bm1TNP mixed leukocyte reaction (MLR), estimated frequencies for precursors of CTL clones that lysed bm1TNP targets ranged from 1/120 to 1/400; in the bm1-anti-B6TNP MLR, estimated frequencies of precursors of CTL clones that lysed B6TNP targets ranged from 1/500 to 1/1,300. Estimated frequencies for precursors of CTL clones that lysed the respective unmodified and TNP-modified allogeneic targets were two- to three-fold lower. Lytic specificity patterns determined by split-well analysis showed that at least 20-30% of the generated CTL populations (selected for a high probability of clonality) in both MLR displayed allorestricted lysis of TNP-modified concanavalin A blast targets. In the B6-anti-bm1HSV MLR, estimated frequencies for precursors of CTL clones that lysed bm1HSV targets ranged from 1/70 to 1/300; in the bm1-anti-B6HSV MLR, estimated frequencies for precursors of CTL clones that lysed B6HSV targets ranged from 1/300 to 1/1,200. Again, estimated frequencies for precursors of CTL clones that lysed the respective noninfected and virus-infected allogeneic targets were two- to fourfold lower. Of the CTL populations selected for a high probability of clonality at least 30-60% displayed allorestricted lysis of virus-infected lipopolysaccharide blast targets in both MLR. It is concluded that a large fraction of clonally developing CTL populations stimulated with TNP-modified or HSV-infected allo-H-2Kb-bearing cells displayed an allorestricted pattern of recognition. It was further evident that the estimated frequencies of splenic precursors that generated allorestricted CTL clones was two- to threefold higher than the estimated frequencies of precursors that gave rise to the respective alloreactive CTL populations.

Alloreactive cytotoxic T cells. I. Alloreactive and allorestricted cytotoxic T cells

Nylon wool-nonadherent spleen cells from three inbred mouse strains of H-2k (CBA), H-2d (BALB/c) and H-2b (C57BL/6) haplotype were co-cultured with 2,4,6-trinitrophenyl (TNP)-modified or nonmodified allogeneic stimulator cells in a limiting dilution system. Using a recently described restimulation protocol, a surprisingly large number of splenic cytotoxic lymphocyte precursors (CLP) was clonally expanded in this primary in vitro response to allo-H-2 plus TNP determinants; measured CLP frequencies ranged from 1/30 to 1/300. The lytic specificity patterns of individual microcultures (selected for a high probability of clonality) were defined by split well analysis, and were furthermore followed up in time by sequentially reassaying microcultures at different time points of in vitro incubation. This analysis revealed the following: a large fraction of cytotoxic T lymphocyte clones lysed TNP-modified but not nonmodified allogeneic concanavalin A blast targets, i.e., were allorestricted; this was found in all 6 allogeneic strain combinations set up with b, k and d haplotype mice; allorestricted lytic patterns predominated in microcultures with low numbers of responder cells per well, and at late time points of in vitro culture; allorestricted lytic cultures were specific for the stimulating allogeneic H-2 plus TNP determinant(s); and allorestricted lytic patterns were also found in microcultures stimulated by nonmodified allogeneic cells. To our knowledge, these are the highest CLP frequencies yet reported in limiting dilution systems that used a specific (re)stimulation protocol and measured the lytic responses obtained in a specificity-controlled readout.

A rapid colorimetric assay for the determination of IL-2-producing helper T cell frequencies

Interleukin 2 (IL-2) activity is tested in conditioned media by assessing its ability to support proliferation of selected IL-2 dependent T cell lines, conventionally measured by [3H]thymidine incorporation. Here, we compare this [3H]thymidine uptake test for measuring IL-2 activity with a rapid and sensitive colorimetric method which is based on the ability of viable cells to cleave 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). The sensitivity of the colorimetric method was dependent on the indicator cell line used, being greatest with the cytotoxic T cell line 16 (CTLL-16). The colorimetric method is at least as sensitive as [3H]thymidine uptake tests, does not rely on radioactivity, and is ideally suited to screen large numbers of individual samples for IL-2 activity. The latter point was demonstrated by calculating IL-2-producing helper T cell frequencies in heterogeneous murine lymphocyte populations: in this assay, splenic T cells were clonally expanded under limiting dilution conditions and supernatants conditioned by these in vitro growing T cell clones were tested for IL-2 activity with the colorimetric method. This allowed us to obtain reliable estimates of the frequency of progenitor cells of IL-2-producing T cell clones in various populations.

Rapid changes in specificity within single clones of cytolytic effector cells

We find rapid changes in the specificity of the cytolytic effector cells in a mixed lymphocyte culture. The lysis patterns produced by cytolytic effector cells generated near limiting dilution in murine mixed lymphocyte reactions of three types, F1 anti-parent (F1(A X B) anti-A), allogeneic (C anti-F1(A X B)), and F1 antimodified parent (F1(A X B) anti-A-TNP), were investigated. Cultures were characterized by their ability or inability to lyse a panel of target cells (e.g., A, B, F1). When individual cultures were tested at two different times, changes in lytic pattern were routinely seen, with some patterns reproducibly increasing in frequency and others reproducibly decreasing (e.g., patterns involving lysis of F1 decreased in an F1 anti-A response but increased in a C anti-F1 response). X-linked isoenzyme analysis showed that changes can occur within a single clone of effector cells. These results imply that the T cell specificity repertoire continues to evolve during an ongoing immune response, a conclusion incompatible with clonal selection theory.

[Metastatic differentiated thyroid cancer. Diagnostic accuracy of thyroglobulin-RIA in comparison with 131I-whole body scintigraphy]

In a retrospective analysis in patients with differentiated thyroid carcinoma, the diagnostic validities of 131I whole-body scans and radioimmunologic determinations of thyroglobulin (hTg) are compared with special regard to late metastases. Metastases were found in 83 out of 311 patients with differentiated thyroid carcinoma. In two thirds of the cases, these were primary metastases while in the remaining third of the cases, metastases developed in later follow-up with a mean time of latency of 3.3 years. While about 70% of the early metastases could bei detected by 131I scintigraphy, this percentage amounted to only 40% in late metastases. With a diagnostic sensitivity of 90%, hTg-RIA was clearly superior in the detection of early as well as of late metastases. hTg was measurable, however, only in iatrogenous hypothyroidism in 4 out of 49 cases. Based on these results and an analysis of the literature, a program for follow-up of differentiated thyroid carcinoma is proposed. The hTg-RIA is thereby used as an alternative to 131I scintigraphy in the late phase of follow-up after complete ablation of any thyroid tissue.

Differential binding of lectins to lymphopoietic and myelopoietic cells in murine marrow as revealed by flow cytometry

Murine marrow cells were labeled with a panel of fluorescein-conjugated lectins and analyzed by flow cytometry. All lectins tested [concanavalin A (Con A), phytohemagglutinin (PHA), wheat germ agglutinin (WGA), pokeweed mitogen (PWM), soybean agglutinin (SBA), peanut agglutinin (PNA), lentil lectin (LL)], stained a fraction of marrow cells; the fraction was, over a defined concentration range, linearly related to the logarithm of the lectin concentration. The slope of this titration curve was characteristic of the particular lectin tested but independent of the nominal sugar specificity of the respective lectin. Con A-, PWM-, and PNA-labeled marrow cells showed brightly and dimly stained subsets in relative fluorescence intensity distribution histograms at high or intermediate staining concentrations. These subsets were composed of cells with restricted and characteristic size distributions as determined by forward light scatter. Lectin staining patterns of marrow cells from normal mice were compared with those of athymic nude mice and mice with severe combined immunodeficiency (SCID). Normal and nude mice lacked a subset of small cells, dimly stained by Con A and PWM, but brightly stained by PNA. This subset, uniquely defined by the above lectins, appears to correspond to the lymphopoietic marrow compartment.

Differentiation from precursors in athymic nude mouse bone marrow of unusual spontaneously cytolytic cells showing anti-self-H-2 specificity and bearing T cell markers

We describe an in vitro limiting dilution culture system that supports growth and differentiation of nylon wool nonadherent bone marrow cells from athymic nude mice. Cells were seeded at low cell numbers (5-120 cells per 20-microliter microculture well) in the absence of added filler or feeder cells but in the presence of conditioned medium. Microwells positive for growth appeared to contain a single clone of cells that adhered together to form a tight cluster referred to here as a colony. A fraction of colonies contained cells that expressed an unusual spontaneous cytolytic activity. They lysed syngeneic or semisyngeneic Con A blast or tumor cell targets but seldom lysed H-2-incompatible Con A blast or tumor target cells, even in a lectin-facilitated assay. A large fraction of colonies contained lymphoid cells that expressed the T cell markers Thy-1 and Lyt-1. Colonies expressing spontaneous cytolytic activity and also containing cells with Thy-1+ and/or Lyt-1+ markers could be grown from nylon wool nonadherent nude marrow cells depleted rigorously by cell sorting of cells expressing either of these markers. Expression of Thy-1 and spontaneous cytolytic activity in a particular colony was significantly correlated. Short-term lines established from cytolytic colonies with T cell markers maintained both characteristics. The cytolytic effector cells observed in these cultures may represent an early stage in the development of the T cell repertoire.

Generation of autoreactive cytotoxic T lymphocytes under limiting dilution conditions

The ability of F1 (H-2k/d) responder cells to generate cytotoxic effector cells against parental and F1 targets was investigated under limiting dilution conditions. One hit limiting dilution curves, consistent with the generated cytolytic cells being the progeny of a single precursor cell, were reproducibly obtained if a culture was scored as "responding" on the basis of its ability to lyse one or more of a panel of Con A blast targets consisting of self F1 and both parents. The calculated frequency of the precursor cell in a nylon wool-nonadherent splenic responder cell population ranged from about 1/500 to 1/1600 in (B10.BR X B10.D2)F1 and (RNC X BALB/c)F1 mice. The patterns of lysis expressed by individual microcultures against the panel of F1 and both parental targets were unusual; besides patterns that were consistent with predictions of classic transplantation rules (i.e., lysis of F1 targets plus one/both parental targets), "anomalous" patterns (i.e., lysis of F1 targets or one/both parental targets exclusively) were also seen. The precursor cells that gave rise to cytolytic cells were devoid of T cell markers, whereas the cytolytic effector cells were Thy-1+, Lyt-2+, as defined by sensitivity to treatment with monoclonal antibody plus complement. The data are discussed in the context of early in vitro development of cytolytic T lymphocytes, with particular emphasis on a possible manifestation of an early T cell repertoire.

Generation of autoreactive cytotoxic T lymphocytes under limiting dilution conditions

The ability of F1 (H-2k/d) responder cells to generate cytotoxic effector cells against parental and F1 targets was investigated under limiting dilution conditions. One hit limiting dilution curves, consistent with the generated cytolytic cells being the progeny of a single precursor cell, were reproducibly obtained if a culture was scored as "responding" on the basis of its ability to lyse one or more of a panel of Con A blast targets consisting of self F1 and both parents. The calculated frequency of the precursor cell in a nylon wool-nonadherent splenic responder cell population ranged from about 1/500 to 1/1600 in (B10.BR X B10.D2)F1 and (RNC X BALB/c)F1 mice. The patterns of lysis expressed by individual microcultures against the panel of F1 and both parental targets were unusual; besides patterns that were consistent with predictions of classic transplantation rules (i.e., lysis of F1 targets plus one/both parental targets), "anomalous" patterns (i.e., lysis of F1 targets or one/both parental targets exclusively) were also seen. The precursor cells that gave rise to cytolytic cells were devoid of T cell markers, whereas the cytolytic effector cells were Thy-1+, Lyt-2+, as defined by sensitivity to treatment with monoclonal antibody plus complement. The data are discussed in the context of early in vitro development of cytolytic T lymphocytes, with particular emphasis on a possible manifestation of an early T cell repertoire.

Lymphoblastogenesis stimulates proliferation of interacting Lyt1 T cells in a syngeneic system

The intravenous transfer of polyclonally activated lymphoblasts elicited a proliferative response of host-derived Lyt1 T cells in the spleens of syngeneic recipient mice. These Lyt1 T cells (responding in vivo to a syngeneic lymphoblast graft) stimulated proliferation of resting, syngeneic splenic Lyt1 T cells, derived from uninjected mice, in a one-way syngeneic mixed lymphocyte culture in vitro. The data are discussed in the context of T cell activation induced by lymphoblastogenesis in a syngeneic system.

Self-reactive T cells. IV. Self-reactive T cells induce polyclonal differentiation of IgM-producing B cells in vivo and in vitro

Intravenous injection of lymphoblasts (generated in vitro by different T- or B-specific mitogens) induced a polyclonal activation of IgM-producing B cells in vivo in the spleens of syngeneic recipient mice. This polyclonal differentiation of host-derived B cells to IgM-producing plaque-forming cells was stimulated by host-derived self-reactive T cells activated in the splenic lymphoid cell population in response to the syngeneic lymphoblast graft. We found a stable factor in the supernatants of cultures of proliferating self-reactive T cells that induced (antigen-independent) polyclonal maturation, but not proliferation of IgM-producing B cells.

Self-reactive T cells. V. T cell-mediated suppression of B cell responsiveness to LPS

The intravenous injection of polyclonally activated lymphoblasts elicited a proliferative T cell reaction in the spleens of syngeneic recipient mice. In the non-fractionated cell populations obtained from these spleens 6 days after lymphoblast transfer, the LPS-induced proliferation and differentiation of B cells in vitro was suppressed. This suppressive effect was mediated by T cells, as i) treatment with anti-Thy-1 antiserum plus complement restored responsiveness of B cells to LPS in the spleen cell population that had responded in vivo to a syngeneic lymphoblast graft, and ii) the responsiveness of B cells to LPS was not impaired in non-fractionated spleen cell populations of nu/nu mice injected with syngeneic lymphoblasts. The relationship of this nonspecific T suppressor cell activity to the previously described non-specific T helper cell activity for B cell activation is discussed.

Studies on T-lymphocyte activation. I. Is competence inductions in thymocytes by phorbol myristate acetate, an accessory cell-independent event?

The effect of phorbol myristate acetate (PMA) on lectin-induced murine thymocyte activation was studied. PMA itself failed to stimulate thymocyte proliferation, but potentiated concanavalin A (Con A)-induced thymocyte activation. A brief incubation of thymocytes with PMA changed the responsiveness of these cells to an optimal mitogenic dose of Con A present during the entire subsequent culture period. Further studies showed that PMA induced in a dose-dependent way within 30 min. an optimal competence of thymocytes to respond to the T-cell growth factor interleukin-2 (IL-2). In contrast to lectin-triggered competence induction, PMA-triggered induction of competence in thymocytes seemed to be independent of accessory cells.

Interleukin-2 allows in vivo induction of anti-erythrocyte autoantibody production in nude mice associated with the injection of rat erythrocytes

Mice injected with rat red blood cells developed anti-erythrocyte autoantibodies detectable by a direct Coombs' test. Nude mice injected with rat red blood cells did not develop a Coombs-positive state, but nude mice injected with rat red blood cells plus the T cell helper factor, interleukin-2, produced autoantibodies to autologous mouse erythrocytes. The simultaneous injection of rat red blood cells and allogeneic spleen cells induced an early and vigorous autoantibody response in athymic nude mice as well as in euthymic control mice. These results are interpreted as indicating the possibility of an interleukin-2-stimulated in vivo differentiation (or clonal expansion) of helper T cells in nude mice in response to heterologous erythrocytes which could mediate an autoimmune B cell response.