H-2 restricted cytolytic and noncytolytic T cell clones: isolation, specificity and functional analysis

The immune response: the afferent arm

The key to understanding afferent immunity is the mechanism of activation of T lymphocytes by specialized antigen presenting cells, which bind antigenic peptide to Class II major histocompatibility molecules, and stimulate T cells via Signal 1 (antigen) and Signal 2 (costimulation). The best studied costimulatory pathway is the interaction of B7-1 or B7-2 ligand molecules on antigen presenting cells with CD28 or CTLA-4 receptors on T cells. T cell signaling occurs through the T cell receptor-CD3 complex and is augmented by cosignaling via CD4, CD8, and CD45. The activation of T cells to alloantigen occurs by either a direct pathway of recognition of allogenic major histocompatibility molecules (with or without an associated endogenous peptide), or by an indirect pathway of recognition of processed donor alloantigens via recipient antigen presenting cells. Afferent immunity on the musculoskeletal system is of special interest because of the absence of viable donor antigen presenting cells in processed grafts that makes them susceptible to the indirect pathway of alloantigen recognition.

CD3 epsilon and CD3 zeta cytoplasmic domains can independently generate signals for T cell development and function

To determine whether CD3 epsilon and CD3 zeta proteins have unique roles in TCR-dependent functions, chimeric genes encoding the extracellular and transmembrane domains of the human IL-2 receptor alpha chain (Tac) fused to a cytoplasmic domain of either the CD3 epsilon or CD3 zeta chain were introduced as transgenes into both normal and RAG2-deficient (RAG2-/-) mice. Developmental arrest of T lineage cells at the CD4, CD8 double-negative stage in the transgenic RAG2-/- thymus was released to the CD4, CD8 double-positive (DP) stage by in vivo cross-linking of TT epsilon or TT zeta with anti-Tac antibody. In TT epsilon + or TT zeta +, RAG2-/- mice, in vitro cross-linking of TT epsilon and TT zeta induced DP thymocyte cell death and proliferation of mature single-positive T cells. Overall, no qualitative differences were observed between TT epsilon- and TT zeta-mediated functions, suggesting that different CD3 components deliver qualitatively similar signals in inducing TCR-dependent functions.

Defective signalling through the T- and B-cell antigen receptors in lymphoid cells lacking the vav proto-oncogene

The product of the vav proto-oncogene, p95vav or Vav, is tyrosine phosphorylated upon stimulation of T and B cells by antigen and other receptors, and contains motifs associated with signal transduction. To determine its role in vivo, we used vav-gene-targeted embryonic stem cells and RAG-2-/- blastocyst complementation. The vav(-/-)-RAG-2-/- chimaeras displayed thymic atrophy with reduced numbers of peripheral T cells. Whereas the total number of B cells was normal, the subset of peritoneal B-1 (CD5+) cells was missing. The vav-/- T and B cells were hyporeactive when stimulated through antigen receptors, but vav-/- T cells proliferated on exposure to phorbol ester and calcium ionophore, whereas B cells responded normally to bacterial mitogen, lipopolysaccharide or the CD40 ligand. Thus, we have established here a functional role for vav in the control of T- and B-cell development and activation.

Development of the CD4 and CD8 lineage of T cells: instruction versus selection

T cells bearing the alpha beta T cell receptor (TCR) can be divided into CD4+8- and CD4-8+ subsets which develop in the thymus from CD4+8+ precursors. The commitment to the CD4 and CD8 lineage depends on the binding of the alpha beta TCR to thymic major histocompatibility complex (MHC) coded class II and class I molecules, respectively. In an instructive model of lineage commitment, the binding of the alpha beta TCR, for instance to class I MHC molecules, would generate a specific signal instructing the CD4+8+ precursors to switch off the expression of the CD4 gene. In a selective model, the initial commitment, i.e. switching off the expression of either the CD4 or the CD8 gene would be a stochastic event which is then followed by a selective step rescuing only CD4+ class II and CD8+ class I specific T cells while CD4+ class I and CD8+ class II specific cells would have a very short lifespan. The selective model predicts that a CD8 transgene which is expressed in all immature and mature T cells should rescue CD4+ class I MHC specific T cells from cell death. We have performed experiments in CD8 transgenic mice which fail to support a selective model and we present data which show that the binding of the alpha beta TCR to thymic class I MHC molecules results in up-regulation of the TCR in the CD4+8+ population. Therefore, these experiments are consistent with an instructive model of lineage commitment.

Mutations in the major histocompatibility complex class I antigen-presenting groove affect both negative and positive selection of T cells

In several transgenic mouse models T cell development was shown to be controlled by the binding of the alpha/beta T cell receptor (TcR) to ligands in the thymus. In transgenic mice expressing a male-specific TcR alpha/beta, the presence of the restricting D major histocompatibility complex (MHC) molecule plus the male specific peptide deleted thymocytes at an early stage of development. On the other hand, maturation of T cells required an interaction of the TcR with the thymic D MHC molecules in the absence of specific peptides. This could imply that negative and positive selection of this receptor are affected differently by mutations in the HY peptide-binding groove of the D MHC molecule. Such mutants have been isolated and were shown to affect the response to HY antigen in that both the bm14 (residue Glu70----Asp) and the bm13 (residue Leu114----Glu, Phe116----Tyr and Glu119----Asp) strains do not normally mount cytotoxic responses to male cells. Here we show that these mutations affect antigenicity of male cells, as well as negative and positive selection of T cells in TcR alpha/beta transgenic mice.

A cell culture model for T lymphocyte clonal anergy

T lymphocytes respond to foreign antigens both by producing protein effector molecules known as lymphokines and by multiplying. Complete activation requires two signaling events, one through the antigen-specific receptor and one through the receptor for a costimulatory molecule. In the absence of the latter signal, the T cell makes only a partial response and, more importantly, enters an unresponsive state known as clonal anergy in which the T cell is incapable of producing its own growth hormone, interleukin-2, on restimulation. Our current understanding at the molecular level of this modulatory process and its relevance to T cell tolerance are reviewed.

Self recognition by T cells. I. Bystander killing of target cells bearing syngeneic MHC antigens

Activated CTL can kill any cell to which they bind or by which they are bound. This observation has been used to determine whether alloreactive CTL can recognize cells bearing self-MHC. When activated by their specific targets, 19 CTL clones of 4 different specificities and origins killed bystander targets bearing syngeneic but not third-party MHC antigens. Using target cells derived from MHC-recombinant animals, syngeneic bystander killing was shown to be restricted to a single self MHC-encoded molecule. These results provide the first clear demonstration that T cells, or more precisely CTL, are capable of self recognition in the absence of their specific antigen. Our findings support the model that T cell repertoire selection occurs as a result of positive selection during maturation in the thymus of precursor cells whose antigen receptors have low but real affinity for self-MHC.

Perforin-dependent and -independent pathways of cytotoxicity mediated by lymphocytes

There is little doubt at the present time that both perforin-dependent and -independent pathways are important in mediating the cytotoxicity associated with lymphocytes. The cell distribution of perforin, initially thought to include both CTL and NK cells, now must be viewed with caution because all previous biochemical studies on CTL have been conducted with cell lines propagated in long-term cultures in the presence of T cell growth factors (IL-2 and perhaps some still undefined factors). Under these conditions, CTL are known to assume a broader, NK-like specificity in target cell killing and may thus differ significantly from primary CTL generated in the body. Accordingly, perforin does not seem to be present in primary CTL activated directly through mixed lymphocyte reactions. It remains to be shown how primary CTL lyse target cells in vivo. Initial studies conducted in several laboratories have already provided some clues. It now seems that even in cultured, perforin-containing CTL, the perforin pathway is not an obligatory mechanism required for target cell killing. Other pathways, possibly involving TNF/lymphotoxin-like molecules, may play a direct role in this type of cytotoxicity. Other still unidentified factors now also need to be sought, including membrane polypeptides that may develop cytotoxicity directly upon cell contact and binding. Although from the studies reviewed here it is clear now that perforin has a more limited role in cell killing than originally proposed, it is still intriguing that it should share structural and functional homologies with complement proteins, drawing paradoxical analogies between two systems (the cellular and the humoral immune systems) which have evolved to become specialized to carry out separate immunological tasks. The cloning of the genes for perforin and for all the C proteins that comprise the MAC should reveal important information on how these genes originated and then diverged during evolution. The cellular distribution of other granule products, such as serine esterases, also must be viewed with caution. A serine esterase activity was initially thought to be CTL-specific. This information stimulated an intensive research activity in many laboratories that resulted in both the purification of a serine esterase family and the cloning of several serine esterase transcripts. It is becoming clear from recent evidence that this group of enzymes is not truly CTL-specific and therefore would not be expected to develop any function rendered absolutely necessary for cytolysis.(ABSTRACT TRUNCATED AT 400 WORDS)

The molecular interactions with helper T cells which limit antigen-specific B cell differentiation

Helper T (Th) cell-dependent activation requirements for 2,4,6-trinitrophenyl (TNP)-specific resting B cells obtained from mice transgenic for Sp-6 mu, kappa genes were analyzed. Carrier-specific T cell help required linked recognition of TNP carrier and was functionally restricted by the B cell major histocompatibility complex. However, histoincompatible T cell-B cell conjugates formed by bridging surface immunoglobulin and Th cell receptor for antigen (TcR) through TNP-conjugated anti-TcR antibodies resulted in the efficient differentiation of TNP-specific B cells. Thus, Th cell-dependent cognate recognition of B cells is not obligatory. Specific conjugate formation could be obviated by using unconjugated fragments of anti-TcR antibodies. If dimeric, these fragments supported the Th cell-dependent differentiation of co-cultured histoincompatible resting B cells. Unconjugated monomeric fragments were ineffective, demonstrating the necessity for TcR cross-linking. Resting B cells from Sp-6+ mice rendered TNP-conjugated monomeric fragments of anti-TcR antibodies effectively multivalent, thereby satisfying conditions for the activation of co-cultured Th cells. The results demonstrate that Th cells do not transduce activation signals through TcR recognition of B cell membrane-associated ligand which limit the induction of B cell differentiation. Cross-linking of TcR on Th cells is required, sufficient and can be induced through interaction with the antigen-specific B cell surface.

Early changes in quiescent B cell physiology subsequent to cognate and bystander interaction with helper T cells

We have assessed early changes in quiescent B cells following cognate and bystander interaction with cloned helper T cells. Variables monitored include Ia expression, blastogenesis, G0 to G1 transition, and progression through cycle. We have also assessed the antigen specificity, Ia restriction, and dependence on membrane immunoglobulin crosslinking of both generation and delivery of effectors that mediate B cell responses. The results demonstrate that antigen presentation by quiescent B cells to T cells resulting in the generation of effectors that activate B cells is Ia-restricted and dependent on antigen and an (mIgM and mIgD) crosslinking signal. However, once generated, T cell effector functions act independently of Ia haplotype to promote Ia expression, blastogenesis, and G0 to G1 transition by most small B cells. Although these responses can be mediated by T cell supernatants, further progression of B cells through S, G2 and M is only efficient when Th cells are present in cultures. Thus, results suggest that one or more Ia unrestricted, labile and/or cell-associated factors, not active in most conventional T cell supernatants, are necessary to stimulate proliferation of small B cells.

Variable capacity of L3T4+ T cells to cause lethal graft-versus-host disease across minor histocompatibility barriers in mice

Highly purified populations of L3T4+ and Lyt-2+ T cell subsets were compared for their capacity to cause lethal GVHD in six different H-2-compatible, multiple minor histocompatibility antigen-different murine strain combinations. In four of these combinations (C3H.SW----B6, DBA/2----B10.D2, B10.BR----CBA, and B10.S----SJL), lethal GVHD appeared to be caused almost entirely by Lyt-2+ cells; the injection of L3T4+ cells resulted in low mortality even when these cells were presensitized to the recipient antigens. In the remaining two combinations (B10.D2----DBA/2 and B10.D2----BALB/c), L3T4+ T cells were able to cause a high incidence of GVHD and were more potent than the Lyt-2+ cells. The implications of these findings are discussed.

Development of natural killer cells in human thymocyte culture: regulation by accessory cells

In vitro culture of human thymocytes resulted in the development of cells with natural killer (NK) activity and the acquisition of a pan-NK antigen (NKH1) by a large number of thymocytes. The ability to kill the NK-sensitive target, K562, was restricted to thymocytes expressing the NKH1 antigen. All NKH1+ thymocytes displayed a mature T cell phenotype, T3+T11+T8+T4-. Both the acquisition of NK activity and the development of cells with the NKH1+ phenotype could be suppressed by culturing thymocytes in the presence of adherent mononuclear cells. These results suggest that adherent accessory cells have the ability to regulate the development of T cell lineage NK cells.

Thymic immune response gene function in radiation chimeras reconstituted with purified hemopoietic stem cells

Thymectomized (C57BL/6[B6] X bm1)F1 mice and thymectomized (B6 X bm12)F1 mice were engrafted with neonatal parental thymus of either B6 type [H-2b mouse, Sendai virus cytotoxic T cell (Tc) responder] or bm1 type (H-2Kb mutant, Sendai virus Tc nonresponder) and B6 type (H-Y Tc responder) or bm12 type (H-2 I-Ab mutant, H-Y Tc nonresponder), respectively. All mice were irradiated and reconstituted with highly purified syngeneic pluripotent hemopoietic stem cells. All types of thymus engraftment resulted in a restored T cell immunocompetence. The Tc reaction to Sendai virus in (B6 X bm1)F1 mice engrafted with both responder type B6 and nonresponder, type bm1 neonatal thymus allowed maturation of Sendai-specific, H-2Kb-restricted Tc. For the Tc reaction to H-Y, only responder type B6 thymus restored the Tc response, whereas this was not achieved with nonresponder type bm12 thymuses. We conclude from this study that in this radiation stem cell chimera system the radioresistant component of the thymus dictates major histocompatibility complex (MHC) specificity and immune response phenotype of T cells restricted to class II MHC molecules but not of T cells restricted to class I MHC molecules.

Characterization of the T3+T4+T8+ thymocyte intermediate in vitro

Sensitive two-color fluorescence staining and cell-sorting techniques were used to isolate a T4+T8+ thymocyte subpopulation with high T3 density from human thymocyte cultures. Previously, this population was shown to give rise to both T4+T8- and T8+T4- thymocytes. In the present study, this T3+T4+T8 population was shown to be functionally as well as phenotypically distinct from either T8+T4- cells or T4+T8- cells present in the same culture. The T3+T4+T8+ cell had intermediate cytotoxic capacities relative to T8+T4- and T4+T8- thymocyte fractions. The proliferative capacity of the T4+T8+ population although less than that of the T8+T4- subset exceeded the proliferative response of the T4+T8- population. The time of appearance of large numbers of T3+T4+T8+ cells in culture as well as functional properties exhibited by T3+T4+T8+ cells are consistent with the notion that the T3+T4+T8+ cell represents an activated intermediate in thymocyte differentiation. The T3+T4+T8+ thymocyte may be an important intermediate in in vivo as well as in in vitro thymic differentiation. Moreover, the analysis of its functional properties may contribute to an understanding of functional responses exhibited by the most mature (T3+) population isolated from human thymus.

Neonatal T cells as a model system to study the possible in vitro senescence of lymphocytes

In this study long-term neonatal T-lymphocyte cultures were initiated from cord blood following alloantigenic stimulation. Growth curves and population doublings were measured for replicate cultures, functional and phenotypic analyses performed, and cells were cloned. Thus, newborn T cells were shown to constitute a potentially excellent model for the analysis of possible in vitro senescence of immunologically relevant cells. Certain problems of the system centering around "crisis" periods and reproducibility, were additionally explored.

A novel cytotoxic T-cell clone that exhibits differential modes of recognition in the proliferative and cytolytic phase

A T-cell clone (1G8-H7) cytotoxic to P815Y mastocytoma (H-2d) has been established from spleen cells of a C3H/He mouse (H-2k) primed with P815Y cells by means of in vitro stimulation with irradiated C3H.H-2o(H-2KdDk) spleen cells. The clone 1G8-H7 was an interleukin 2 (IL-2)-dependent and H-2Kd antigen-dependent CTL clone and it killed P815Y cells but not Concanavalin A-induced spleen blast cells bearing H-2Kd antigen. The involvement of H-2Kd antigen in the cytolytic recognition mechanism was shown by the inhibition of lysis by anti-H-2Kd monoclonal antibody and also by the cold inhibition experiment that employed H-2Kd-bearing spleen cells. Comparison of cytotoxic activities between 1G8-H7 and Kd-specific CTL clones showed that the killing of P815Y cells by clone 1G8-H7 was not explained by the susceptibility to cell-mediated cytolysis of P815Y cells. These results suggest that H-2Kd antigen on the stimulating cell is sufficient to deliver a proliferation signal in the proliferative phase of this clone, but in the cytolytic phase an additional interaction with surface structure on the target cell other than that with H-2Kd antigen is required for the induction of cytolysis. Possible elucidations for the differential modes of recognition are discussed.

Cooperation between cytotoxic and helper T lymphocytes in protection against lethal Sendai virus infection. Protection by T cells is MHC-restricted and MHC-regulated; a model for MHC-disease associations

The in vivo importance of class I MHC regulation of the Tc response to a natural pathogenic agent of high virulence was studied on the basis of our previous demonstration of a major difference in the capacity to generate a Sendai virus-specific Tc response between C57BL/6 (B6, H-2b) mice and H-2Kb mutant B6.C-H-2bm1 (bm 1) mice. These two mouse strains differ from each other only in three amino acids in the crucial H-2Kb restriction element for this response. bm 1 mice, in contrast to B6 mice, are Tc nonresponders against this virus, but show Sendai-specific T cell proliferation, antibody production, and DTH reactions, as well as NK cell activity, equal to those of B6 mice. B6, Sendai Tc-deficient bm 1 and T cell-deficient B6 nu/nu mice differ from each other in susceptibility to lethal pneumonia induced by i.n. inoculation of virulent Sendai virus. The lethal dose (LD50) in B6 mice averaged 152 TCID50, in bm 1 mice, 14 TCID50 and in B6 nu/nu mice 0.5 TCID50. The importance of Tc was also shown by the complete protection of B6 nu/nu mice against infection with a lethal virus dose by i.v. injection of a Sendai virus-specific, IL-2-dependent and H-2Kb-restricted B6 Tc clone. In vivo protection by this Tc clone was H-2Kb-restricted. Apart from Tc, an important role for virus-specific Th cells is evident from the difference in susceptibility between bm 1 and B6 nu/nu mice. This conclusion was supported by the demonstration that the mean survival time of B6 nu/nu and bm 1 nu/nu mice could be significantly prolonged, in an I-Ab-restricted manner, by the injection of in vitro-propagated, Sendai-specific B6 or bm 1 Th clones after a lethal dose of Sendai virus, and by the demonstration that inoculation of these Th clones provided help to virus-specific Tc by means of IL-2 production. Strikingly, Th and Tc cooperate in anti-Sendai virus immunity, since permanent survival of lethally infected nu/nu mice was only achieved by inoculation of a mixture of Tc and Th clones or a mixture of a Tc clone and rIL-2. This study provides a unique model for the study of MHC-disease associations.

Discrete stages of human thymocyte activation and maturation in vitro: correlation between phenotype and function

Using light scatter, flow cytometric and functional analyses, three major stages in the in vitro activation of human thymocytes were defined. The earliest stage (day 0-2) was characterized by the induction of the interleukin 2 (IL2) and transferrin receptors, the T cell lineage specific Ta1 antigen, and increased reactivity with anti-T8 antibody. At this time, major changes in nuclear morphology but not cell size were observed. Early-stage thymocytes were immature with regard to T3 and cytotoxic capacities. The second stage (day 3-4) of in vitro culture was distinguished by loss of T6, maximal activation (both in cell size and nuclear morphology) and maximal expression of both transferrin and IL2 receptors. At this stage, nearly all thymocytes expressed T3, 30-70% of thymocytes were T4+T8+, and functionally, only small increases in cytotoxic capacities were observed. The third stage of maturation (day 5-7) represented thymocytes with reduced levels of activation as measured by forward and right angle light scatter analysis and declining IL2 and transferrin receptor expression. However, these thymocytes exhibited high levels of T3 antigen density, loss of T4, T8 coexpression and pronounced cytotoxic and detectable inducer function capabilities.

Functions of purified L3T4+ and Lyt-2+ cells in vitro and in vivo

The expression of L3T4 and Lyt-2 cell surface molecules separates T cells into two broad, non-overlapping subsets: typical T helper cells are L3T4+ Lyt-2- whereas most T killer cells and their precursors are L3T4- Lyt-2+. This review compares highly purified populations of unprimed L3T4+ and Lyt-2+ cells for their capacity to respond to class I vs. class II H-2 alloantigens. Various parameters are considered, including generation of mixed lymphocyte reactions (MLR) and cell mediated lympholysis (CML) in vitro, proliferative responses in irradiated mice, graft-versus-host reactions and skin allograft rejection. In all of these assays the two T cell subsets exhibit marked specificity in their response to H-2 alloantigens, L3T4+ cells responding only to class II and not class I differences and Lyt-2+ cells showing reciprocal specificity. Contrary to current dogma, the bulk of the evidence suggests that primary responses of Lyt-2+ cells do not depend on exogenous help provided by other T cells.

Characterization of a tumorigenic murine T-lymphoid-cell line spontaneously derived from an IL-2-dependent T-cell line

The establishment of IL-2-independent T-cell lines spontaneously derived from long-term IL-2-dependent cytotoxic T-cell lines is described. Two lines (cloned and uncloned) studied in detail have shown the following characteristics: (1) Permanent loss of IL-2 dependence. (2) Partial or complete loss of both cytotoxic activity and the IL-2 receptor. (3) Increased expression of T-cell membrane markers (Thy1.2, Lyt1.2) compared with the parental line. (4) Lower level of DNA methylation than in freshly obtained lymphoid cells. (5) Different karyotypic pattern from the parental IL-2-dependent line, with a mean number of 39-40 chromosomes and a resemblance to T leukemic lines. (6) Leukemia caused in normal syngeneic C57BL/6 mice by the uncloned line, in contrast to the cloned IL-2-independent line or the parental dependent line. Unlike established leukemic lines, however, the independent line gave rise to tumors which regressed in some mice within a few days of their appearance. These findings suggest that T-cell lines maintained with IL-2 for prolonged periods of time (greater than 3 months) can undergo transformation and, therefore, should not be utilized for immunotherapeutic purposes.

Use of a P815-derived line with an amplified adenosine deaminase gene: an improved target for cellular cytotoxicity

We describe a cytotoxic T lymphocyte-mediated cytotoxicity assay in which the release of a cytoplasmic enzyme, adenosine deaminase (ADA), instead of the widely used radioactive chromium is a measure of target lysis. In this enzyme-release assay the target is a mastocytoma P815-derived cell line, noted P815 ADA++, isolated by applying a selection procedure devised to specifically amplify the ADA gene. Gene amplification in P815 ADA++ was indeed demonstrated. Routine measurement of ADA activity from numerous supernatants is performed using a specific and sensitive colorimetric assay. The use of 96-well microtiter plates as well as of an automatic Multiscan spectrophotometer makes this measurement rapid and convenient. We show that this ADA-release assay is significantly more sensitive than the classical chromium-release test because of its consistently lower (5 to 10-fold) spontaneous release in 4 h, short-term cytotoxicity experiments. We also found that it is especially suited for the rapid detection, by visual screening, of rare, active killer clones among large, heterogeneous cytotoxic T lymphocyte populations. The assay could easily be adapted to other tumor targets (EL4, YAC-1, K562) of common use in studies involving immune lysis; indeed, the procedure of amplifying the ADA gene used in the isolation of the P815 ADA++ hyperactive line may be generally applied to these targets.

Cytolytic T cell hybridomas. III. The antigen specificity and the restriction specificity of cytolytic T cells do not phenotypically mix

We have obtained cytolytic T-T hybrids by fusing an H-2Kk restricted clone specific for the hapten 3-(p-sulfophenyldiazo)-4-hydroxyphenyl acetic acid (SP) with an H-2Dd-restricted clone specific for the hapten fluorescein (FL). Several hybrid clones express both parental specificities but fail to lyse SP-coupled H-2Dd and FL-coupled H-2Kk target cells. We also fused the H-2Kk-restricted, SP-specific clone with a clone which recognizes FL in the context of any class I major histocompatibility complex antigen. Again several hybrids show both parental specificities but fail to recognize SP coupled to target cells which are not recognized by the parental SP-specific clone. These findings indicate that the observed cytotoxic T lymphocyte specificities for haptens on the one hand and polymorphic as well as nonpolymorphic class I major histocompatibility complex antigenic determinants on the other hand are not carried by independent proteins.

The human lymphokine-activated killer cell system. V. Purified recombinant interleukin 2 activates cytotoxic lymphocytes which lyse both natural killer-resistant autologous and allogeneic tumors and trinitrophenyl-modified autologous peripheral blood lymphocytes

Culture of human peripheral blood lymphocytes (PBL) in purified natural or recombinant interleukin 2 in the absence of exogenous antigen or mitogen causes the differentiation of nonlytic precursor cells into lymphokine-activated killers (LAK). A titration of purified Jurkat IL-2 (BRMP, FCRC, NIH) IL-2 showed that the relatively low concentration of 5 U/ml was optimal for LAK activation. When the responding PBL were pretreated with either mitomycin C or gamma irradiation, LAK activation did not occur, indicating that proliferation, in addition to differentiation, is required. The spectrum of target cells susceptible to LAK lysis in a 4-hr chromium-51-release assay includes fresh NK-resistant tumor cells and trinitrophenyl (TNP)-modified autologous PBL. Unmodified PBL are not lysed. Cold target inhibition studies indicated that LAK lysis of autologous TNP-PBL is totally inhibited by fresh tumors cells, and that tumor lysis is inhibited by TNP-PBL. Additionally, allogeneic tumors totally inhibit lysis of autologous tumor cells in other cold target studies. These results demonstrate that the lytic activity expressed by LAK is not HLA restricted, is not limited to tumor cells, and is "polyspecific" as indicated by the cross-reactive recognition of multiple target cell types in these cold target inhibition studies.

Clonal specificity of concanavalin A-induced cytotoxic T lymphocytes

The specificity of polyclonally induced cytotoxic T lymphocyte (CTL) precursors has been analyzed under clonal conditions. Primary clones of concanavalin A-inducible CTL, if tested on different targets, revealed that they could distinguish between (a) two different allogeneic tumor targets; (b) allogeneic and syngeneic tumor targets, and (c) syngeneic B blasts and tumor targets. No "nonspecific" CTL clones were generated under these culture conditions, and all clones were found to display classical immunological specificity.

Limited diversity of the rearranged T-cell gamma gene

The immunoglobulin-related, T-cell specific gamma gene is rearranged in a wide variety of murine T lymphocytes. We detected gamma-gene transcripts in all cloned cytotoxic T lymphocytes examined but in only 1 of 11 T-helper cell lines or hybridomas. Although in cytotoxic T cells, the rearranged gamma gene seems to have been assembled from the same germ-line variable and joining gene segments, the transcribed gene exhibited distinct sequence diversity near the junction between these segments.

Interleukin 2 induces synthesis of polypeptides in an interleukin 2-dependent cell line by transcription and translation

Interleukin 2 (IL 2) is a lymphocyte growth factor capable of inducing the rapid growth of antigen- or mitogen-stimulated T cells. To understand the molecular mechanisms of IL 2 action, we studied the synthesis of cellular polypeptides induced by IL 2. For a homogeneous cell population responsive to IL 2, we used a murine clone of natural killer-like cells, NK 7, which is strictly dependent on exogenous IL 2 for cell viability and growth. NK 7 cells were first kept in culture without IL 2 for 6 h and then labeled for 3 h with [14C]leucine in the presence or absence of 100 U/ml recombinant human IL 2. Analysis of the cellular polypeptides by two dimensional gel electrophoresis and autoradiography revealed that the addition of IL 2 to IL 2-starved NK 7 cells specifically increased the levels of at least ten polypeptides (designated from molecular weight as p94a, p94b, p52, p51a, p51b, p48.5, p36, p34.5, p25.5, and p23). The increases of p52, p25.5, and p23 were inhibited by 5 micrograms/ml actinomycin D, whereas the other seven were virtually unaffected by the drug.

Thymus dictates major histocompatibility complex (MHC) specificity and immune response gene phenotype of class II MHC-restricted T cells but not of class I MHC-restricted T cells

Athymic H-2b nude mice received grafts from C57BL/6 (Sendai virus and H-Y antigen cytotoxic T lymphocyte [CTL] responder type), bm1 (H-2Kb mutant, Sendai CTL nonresponder type), or bm12 (H-21-A mutant, H-Y CTL nonresponder type) neonates. In observations of the CTL response to H-Y, both recipients and thymus donors were female. All types of thymus engraftment resulted in mature H-2b splenic T lymphocyte surface phenotype in nude hosts. T cell immunocompetence (as measured by major histocompatibility complex [MHC] CTL responses to allogeneic cells) was restored, and induced nonresponsiveness to the MHC determinants of the engrafted thymus in the nude host. The CTL reaction to Sendai virus in both responder type C57BL/6 and nonresponder type bm1 neonatal thymuses allowed maturation of Sendai-specific, H-2Kb-restricted CTL. For the CTL reaction to H-Y, only responder type C57BL/6 thymuses restored the CTL response, whereas this was not achieved with thymuses from nonresponder type bm12 neonatal females. Results of double thymus (B6 and bm12) engraftment excluded the possibility that this latter effect was caused by suppression. In addition, athymic bm1 mice were engrafted with thymuses from either B6 (Sendai CTL responder type) or syngeneic bm1 neonates (Sendai CTL nonresponder type). Again, both types of neonate thymuses restored T cell competence as measured by MHC/CTL responses to allogeneic cells. However, neither responder B6 nor nonresponder bm1 neonate thymus grafts allowed maturation of Sendai-specific CTL. In conclusion, the thymus dictates MHC specificity and immune response gene phenotype of T cells restricted to class II MHC molecules but not of T cells restricted to class I MHC molecules.

A colorimetric assay for serial determination of adenosine deaminase activity in small lymphocyte populations

We describe here an easy, sensitive and quantitative assay for the determination of adenosine deaminase activity in small populations of lymphoid cells. Determinations of enzyme activity and protein concentration are based on colorimetric reactions. All steps are directly performed in 96-well flat-bottom microtiter plates: growth of lymphoid cells (1-2 X 10(5) cells needed), detergent-mediated lysis, incubations for enzymatic assay, and reading of colorimetric reactions with an automatic multiscan spectrophotometer. Thus, screening of several hundred independent cell cultures is easily done within a day. Applications to the detection of rare adenosine deaminase variants from large cell populations and to routine medical assays are considered.

Isolation of cDNA clones encoding T cell-specific membrane-associated proteins

Of 10 distinct cloned DNA copies of mRNAs expressed in T lymphocytes but not in B lymphocytes and associated with membrane-bound polysomes, one hybridizes to a region of the genome that has rearranged in a T-cell lymphoma and several T-cell hybridomas. These characteristics suggest that it encodes one chain of the elusive antigen receptor on the surface of T lymphocytes.

HLA class I specific T lymphocyte clones with dual alloreactive functions

Four human T lymphocyte clones exhibiting proliferative responses to class I HLA antigens were isolated from an in vitro mixed lymphocyte culture (MLC). Three clones expressed the Leu-2+3- phenotype and demonstrated proliferation in response to HLA-B8, while the fourth clone expressed the Leu-2-3+ phenotype and proliferated in response to HLA-A2. These clones were also cytotoxic towards cells bearing the same target antigens. Blocking studies utilizing monoclonal antibodies demonstrated that proliferation was triggered by determinants on the class I molecule itself, and these determinants appear to be spatially close to those which determine serologic allospecificity. These findings support the concept that the class I molecules themselves are the weak MLC stimulating determinants previously mapped to the HLA-A and B regions of the major histocompatibility complex.

Alloreactive T cell clones

T cell clones are useful models for studying lymphocyte function both at the level of the individual cell and in interacting systems. Murine cytolytic and non- cytolyic T cell clones have been obtained with relative ease, and the particular procedure used to derive and maintain T cell clones may influence profoundly the characteristics of the resulting cells. The method of choice depends on the specific question to be asked. Although some clones have characteristics that would have been expected on the basis of results observed with bulk cell populations, other clones have rather unexpected properties. Although most T cell clones appear to be either cytolytic or non-cytolytic, this distinction is not always absolute. A high proportion of both cytolytic and non-cytolytic T cell clones have dual reactivity. This is true for cells which by other criteria appear to be true clones. The frequency of such cells is high enough to suggest that most if not all T cells may have reactivity for more than one antigenic determinant or that antigenic determinants recognized by T cells are shared widely and unexpectedly. It is not clear whether one or two different antigen receptors account for such dual reactivity. The nature of the T cell receptor for antigen remains obscure. T cell clones, because of their homogeneous nature, should make it easier to answer these important immunological questions. Although it remains to be determined how many distinct molecules account for the numerous biological activities found in the culture supernatants from antigen-stimulated T cell clones, it is clear that these factors influence several different types of cells that are involved directly and indirectly in immune responses. IL-2 stimulates both cytolytic and non-cytolytic T cells to proliferate. BCSF causes polyclonal activation of B cells, and there may be other factors which influence B cell responses to antigenic stimulation. IL-3 apparently stimulates maturation of immature T cells. CSF stimulates production of macrophages from precursor cells found in the bone marrow. Supernatants also stimulate expression of Ia antigens by macrophages, and antigen-presenting cells have been found to bear Ia antigens. Interferon augments natural killer cell activity. Thus, regardless of how many molecules are involved in these effects, activated non-cytolytic T cells appear to be involved in a variety of ways in the modulation of immune responses.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunological surveillance of tumors in the context of major histocompatibility complex restriction of T cell function

The immunological surveillance hypothesis was formulated prior to the realization of the fact that an individual's effector T cells generally only see neoantigen if it is appropriately presented in the context of self MHC glycoproteins. The biological consequence of this mechanism is that T lymphocytes are focused onto modified cell-surface rather than onto free antigen. The discovery of MHC-restricted T cell recognition, and the realization that T cell-mediated immunity is of prime importance in promoting recovery from infectious processes, has thus changed the whole emphasis of the surveillance argument. Though the immunological surveillance hypothesis generated considerable discussion and many good experiments, there is no point in continuing the debate in the intellectual context that seemed reasonable in 1970. It is now much more sensible to think of "natural surveillance" and "T cell surveillance," without excluding the probability that these two systems have elements in common. We can now see that T cell surveillance probably operates well in some situations, but is quite ineffective in many others. Part of the reason for this may be that the host response selects tumor clones that are modified so as to be no longer recognized by cytotoxic T cells. The possibility that this reflects changes in MHC phenotype has been investigated, and found to be the case, for some experimental tumors. In this regard, it is worth remembering that many "mutations" in MHC genes that completely change the spectrum of T cell recognition are serologically silent. The availability of molecular probes for investigating the status of MHC genes in tumor cells, together with the capacity to develop cloned T cell lines, monoclonal antibodies to putative tumor antigens, and cell lines transfected with genes coding for these molecules, indicates how T cell surveillance may profitably be explored further in both experimental and human situations.

Fine specificity of the immune response to oxazolones III. Antibodies but not contact sensitivity specific for 2-furyloxazolone are controlled by an Igh-V gene in the mouse

Early IgM and IgG antibodies of CBA and C3H mice (Igh allotype j) against furyloxazolone (furyl Ox) were found to be heteroclitic, they had a 4-6 times higher affinity for styryloxazolone (styryl Ox) than for furyloxazolone. Anti-furyl Ox antibodies of six other strains (Igh allotypes a, b, c, e, f or g) had approximately 100 times higher affinity for furyl Ox than for styryl Ox. The heteroclitic fine-specificity was inherited as an Igh allotype-linked trait. Furyl Ox-specific contact sensitivity was induced by painting, and its specificity was studied with a recently developed method (Ferreira et al., J. Immunol. 1981. 127:2366). Small strain differences in specificity were detected. They were not inherited as an Igh allotype-linked trait.

Differential requirements for activation and growth of unprimed cytotoxic and helper T lymphocytes

The requirements for activation and growth of T lymphocytes capable of mediating either cytolytic activity or help to B lymphocytes were studied in unprimed splenic T cell populations. The selectivity of expression of Lyt-2 antigens, the reactivity to soluble concanavalin A (Con A), to partially purified interleukin 2 (IL 2, T cell growth factor[s]) and to lectin-pulsed macrophages (M phi) were used in this analysis. Lectin-dependent cytotoxicity assays and a novel method that allows for the detection of all effector helper cells, regardless of their clonal specificities, were used for the functional identification of the responding T cells. The results show a marked contrast between cytolytic and helper T cells in their growth and activation requirements. Thus, while Lyt-2+ cytotoxic T lymphocyte precursors grow exponentially in IL 2 after a short pulse with soluble Con A in the absence of accessory cells, Lyt-2- helper cell precursors completely fail to proliferate under the same conditions and require the continuous presence of lectin-pulsed M phi for significant growth. Furthermore, addition of IL 2 to M phi-stimulated cultures of Lyt-2- cells has no effect. T cells which produce IL 2 have the same growth characteristics as helper cells. In both cases, effector helper functions could be expanded more than 10-fold on a per cell basis by a 5-day-culture period under those growth supporting conditions. The development of effector helper functions, however, was strongly inhibited by the presence of Lyt-2+ T cells.

Activation of helper T cells for B lymphocytes in primary mixed lymphocyte cultures

Normal B10.BR (H-2k, C57B1/6 background) spleen cells, enriched in primary mixed lymphocyte culture (MLC) for antigens of C3H/Tif mice (H-2k, C3H background), induced normal C3H/Tif but not B10.BR B lymphocytes to proliferate and produce Ig. In contrast, normal B10.BR spleen cells enriched in parallel B10.BR anti-C57B1/6 (H-2b) MLC were not able to activate either B10.BR or C57B1/6 B lymphocytes. However, normal B10.BR spleen cells depleted of Lyt2+ cells before initiation of the MLC, and subsequently enriched either for C3H/Tif or C57B1/6 antigens, activated B lymphocytes of the respective mouse strains specifically and equally well. These experiments show that primary MLC gives rise to effector T helper cells that, on recognition of specific alloantigens, activate normal B lymphocytes of the 'stimulator' strain. In response to major histocompatibility complex (MHC) alloantigens, this help is not revealed because of interference by Lyt 2+ lymphocytes. MHC-reactive T helper cells for B lymphocytes, however, participate in these reactions and constitute the predominant population in long-term cultures that are maintained by consecutive in vitro restimulations.

The ontogeny of T lymphocytes

We have provided a speculative overview of some of the questions concerning the nature of thymic stem cells and the role of the thymus in their maturation, and have suggested experimental approaches which might provide solutions to some of the questions. Throughout, we have stressed the complexity of the cellular constitution of the thymus and have suggested roles for particular cell types which seem plausible based on present evidence.

Human normal CTL clones: generation and properties

This study reports the production of clones of human killer T cells grown in the presence of TCGF4 following sensitization in MLC against (1) allogeneic cells, (2) autologous Bebv+ lymphocytes, or (3) autologous lymphoma cells. Sensitization against the tumor cells required the addition of macrophages. The expression of the cytotoxic activity of the cloned T lymphocytes required re-stimulation with the specific stimulator cells. The cytotoxic activity seemed to be MHC-restricted, since (1) cloned allosensitized CTL lysed their corresponding allogeneic targets, but did not lyse autologous Bebv+ cell or K562 cells; (2) cloned CTL sensitized against autologous Bebv+ cells lysed their autologous targets but not allogeneic Bebv+ targets or K562 cells; and (3) cloned CTL sensitized against autologous Burkitt lymphoma cells lysed their corresponding lymphoma targets or autologous Bebv+ targets but did not lyse allogeneic lymphoma cells or Bebv+ cells from the same allogeneic lymphoma cells or Bebv+ cells from the same allogeneic donors. The cloned CTL were homogeneous in expressing the OK T8 molecules and in being negative for T4, T10 or M1. At any given time, 25-45% of the cloned cells manifested lytic activity. The ultrastructural properties and cell surface OK T markers were different from those of cloned human NK cells. Emphasis is focused on the differences between the structural, functional and culture characteristics of CTL clones produced by direct isolation of MLC responder cells forming conjugates with specific target cells and those of clones from transformed T-cell lines or from T hybridomas.

Lethal GVHD across minor histocompatibility barriers: nature of the effector cells and role of the H-2 complex

Transfer of T-cells to heavily irradiated, H-2-compatible mice frequently leads to a high incidence of lethal graft-versus-host disease (GVHD). Lymphoid cells depleted of Thy1+ cells fail to cause GVHD. Studies with a variety of different, H-2-compatible, strain-combinations suggest that minor, histocompatibility antigens (minor HA) are the main targets for eliciting lethal GVHD. Experiments in which T-cells are negatively selected to minor HA by acute blood-to-lymph recirculation through irradiated hosts have indicated that the T-cells eliciting GVHD to minor HA, are H-2-restricted. In H-2-compatible hosts, the donor T-cells recognize the minor HA of the host and become temporarily trapped in the lymphoid tissues for 1-2 days; during this stage of negative selection, the donor T-cells entering the lymph are specifically devoid of cells able to elicit GVHD against the host, minor HA on further transfer. When the selection host is H-2-different with respect to the donor T-cells, by contrast, the T-cells ignore the host, minor HA and negative selection fails to occur. The T-cells recirculate normally and are unimpaired in their capacity to elicit GVHD on further transfer. By the use of various H-2-recombinant mice as selection hosts it has been shown that, as for T-cells exerting cell-mediated lympholysis (CML) to minor HA in vitro, the T-cells which elicit lethal GVHD to minor HA comprise two distinct subsets of H-2-restricted cells. One subset recognizes minor HA in the context of H-2K (or K end) molecules whereas the other is specific for minor HA-plus-H-2D. Curiously, in marked contrast to the findings on CML responses in vitro, no evidence has been found that H-2I-restricted T-cells contribute to GVHD, either as effector cells or as helper cells. Purified populations of Lyt 1-2+ T-cells have potent GVHD activity, whereas Lyt 1+2- cells fail to cause GVHD. Studies with various types of bone-marrow chimeras suggest that in the induction phase, T-cells recognize minor HA only on lymphohematopoietic cells. In the effector phase, by contrast, non-marrow-derived cells appear to be the main targets of attack. Although the pathogenesis of GVHD is poorly understood, the lethal form of the disease probably reflects the penetration of mucosal surfaces by pathogenic organisms, perhaps as the result of direct destruction of epithelial cells by minor HA-specific cytotoxic lymphocytes. Direct support for this notion has yet to be obtained.

Generation of cytotoxic T lymphocytes against modified self in the absence of antigen by interleukin 2-containing preparations

Spleen cells obtained from normal mice were cultured with interleukin 2 (IL2); no antigen was added. After 4-5 days, these cultures contained effector cells which lysed autologous spleen target cells that were modified with 2,4,6-trinitrobenzene sulfonic acid or fluorescein isothiocyanate. No killing was seen on unmodified spleen target cells. These effector cells were Thy 1+, Lyt 1-, 2+ and were derived from Thy 1+ precursor cells. IL2 preparations induced the generation of such cytotoxic T lymphocytes (CTL) in a dose-dependent manner. IL2-induced CTL were shown to be different from the natural killer (NK) cells augmented by IL2 by virtue of their time of appearance in culture, by cold-target competition, and by different cell-surface markers. These results demonstrate that the IL2 signal may be sufficient for the induction of the differentiation of CTL precursors in the absence of an antigenic signal.