Specific enrichment of the suppressor T cell bearing I-J determinants: parallel functional and serological characterizations

The Role of Regulatory T Cells in Epicutaneous Immunotherapy for Food Allergy

In recent decades, a rapid increase in the prevalence of food allergies has led to extensive research on novel treatment strategies and their mechanisms. Mouse models have provided preliminary insights into the mechanism of epicutaneous immunotherapy (EPIT)-induced immune tolerance. In EPIT, antigen applied on the skin surface can be captured, processed, and presented in the lymph nodes (LNs) by Antigen-presenting cells (APCs). In the LNs, induction of regulatory T cells (Treg cells) requires both direct contact during antigen presentation and indirect mechanisms such as cytokines. Foxp3+CD62L+ Treg cells can exhibit the characteristics of hypomethylation of Foxp3 TSDR and Foxp3-LAP+ Treg cells, which increase the expression of surface tissue-specific homing molecules to exert further sustained systemic immune tolerance. Studies have shown that EPIT is a potential treatment for food allergies and can effectively induce immune tolerance, but its mechanism needs further exploration. Here, we review Treg cells' role in immune tolerance induced by EPIT and provide a theoretical basis for future research directions, such as the mechanism of EPIT and the development of more effective EPIT treatments.

Regulatory T-cells: diverse phenotypes integral to immune homeostasis and suppression

Regulatory T-cells (T(REG)) are diverse populations of lymphocytes that regulate the adaptive immune response in higher vertebrates. T(REG) delete autoreactive T-cells, induce tolerance, and dampen inflammation. T(REG) cell deficiency in humans (i.e., IPEX [Immunodysregulation, Polyendocrinopathy and Enteropathy, X-linked syndrome]) and animal models (e.g., "Scurfy" mouse) is associated with multisystemic autoimmune disease. T(REG) in humans and laboratory animal species are similar in type and regulatory function. A molecular marker of and the cell lineage specification factor for T(REG) is FOXP3, a forkhead box transcription factor. CD4(+) T(REG) are either natural (nT(REG)), which are thymus-derived CD4(+)CD25(+)FOXP3(+) T-cells, or inducible (i.e., Tr1 cells that secrete IL-10, Th3 cells that secrete TGF-β and IL-10, and Foxp3(+) Treg). The proinflammatory Th17 subset has been a major focus of research. T(H)17 CD4(+) effector T-cells secrete IL-17, IL-21, and IL-22 in autoimmune and inflammatory disease, and are dynamically balanced with T(REG) cell development. Other lymphocyte subsets with regulatory function include: inducible CD8(+) T(REG), CD3(+)CD4(-)CD8(-) T(REG) (double-negative), CD4(+)Vα14(+) (NKT(REG)), and γδ T-cells. T(REG) have four regulatory modes of action: secretion of inhibitory cytokines (e.g., IL-10 and TGF-β), granzyme-perforin-induced apoptosis of effector lymphocytes, depriving effector T-cells of cytokines leading to apoptosis, or inhibition of dendritic cell function. The role of T(REG) in mucosal sites, inflammation/infection, pregnancy, and cancer as well as a review of T(REG) as a modulatory target in drug development will be covered.

Human chorionic gonadotropin as a model for a fetal antigen

Human chorionic gonadotropin (hCG) has an important biological function and has clinical use as a hormone, yet its applications as an antigen are also numerous. Pregnancy tests have brought immunological reactions into the high street pharmacy and the home. As a secreted antigen hCG provides for choriocarcinoma of gestational or germ cell origin our closest approximation to the ideal tumour marker. It is unique in providing the basis of a biochemical screening test for a specific cancer in a high risk population. It has a valuable role in diagnosis and prognosis and in monitoring this disease and detecting tumours is unknown. It has been investigated as a target for radioimmunolocalization studies with 131I-labelled anti-hCG antibodies, and found useful in some patients. Attempts have been made to improve the technique using liposomes containing a second antibody. As a target for antibody therapy in fertility control and oncology, by active or passive immunization methods, much depends on whether hCG functions as a cell membrane antigen.

CD8+CD122+ regulatory T cells recognize activated T cells via conventional MHC class I-alphabetaTCR interaction and become IL-10-producing active regulatory cells

CD8(+)CD122(+) regulatory T cells (CD8(+)CD122(+) Treg) are naturally occurring Treg that effectively suppress the proliferation and IFN-gamma production of both CD8(+) and CD4(+) target cells. This study investigated the molecular mechanisms of the recognition of target cells by CD8(+)CD122(+) Treg using an in vitro culture system that reconstitutes the regulatory action of these cells. Naive CD8(+)CD122(+) Treg co-cultured with pre-activated T cells became active Treg that produced IL-10 and suppressed IFN-gamma production from the target T cells. CD8(+)CD122(+) Treg effectively suppressed the IFN-gamma production of the target cells of syngeneic mouse strains but not of allogeneic mouse strains with incompatible MHC. By using MHC-congeneic mouse strains, MHC-restricted suppression by CD8(+)CD122(+) Treg was further confirmed. The blockade of cell surface molecules either on the Treg or on the target cells by specific blocking antibodies indicated that H-2K, H-2D, alphabetaTCR and CD8 were involved in the regulatory action but I-A and Qa-1 were not. These results indicate that CD8(+)CD122(+) Treg recognize already-activated T cells via the interaction of conventional MHC class I-alphabetaTCR and become active regulatory cells that produce IL-10 and suppress the target cells.

Special regulatory T-cell review: Regulation of immune responses--examining the role of T cells

The history of regulatory T cells goes back to the realisation that T cells could provide 'help' for antibody responses: the obverse of this is their ability to hold them in check. This brief personal overview follows the initial designation of T cells as 'suppressor' and the various hypotheses, some now disproved, put forward for their mechanism of action. We now cautiously label them T regulatory cells, but realise they do not control not all immune regulation. They probably operate through several mechanisms, and some of these are discussed.

Special regulatory T-cell review: A rose by any other name: from suppressor T cells to Tregs, approbation to unbridled enthusiasm

In the early 1970s a spate of papers by research groups around the world provided evidence for a negative regulatory role of thymus-derived lymphocytes (T cells). In 1971, Gershon and Kondo published a seminal paper in Immunology entitled 'Infectious Immunological Tolerance' indicating that such negative regulation could be a dominant effect that prevented otherwise 'helpful' T cells from mediating their function. Over the next decade, suppressor T cells, as these negative regulatory cells became known, were intensively investigated and a complex set of interacting cells and soluble factors were described as mediators in this process of immune regulation. In the early 1980s, however, biochemical and molecular experiments raised questions about the interpretation of the earlier studies, and within a few years, the term 'suppressor T cell' had all but disappeared from prominence and research on this phenomenon was held in poor esteem. While this was happening, new studies appeared suggesting that a subset of T cells played a critical role in preventing autoimmunity. These T cells, eventually dubbed 'regulatory T cells', have become a major focus of modern cellular immunological investigation, with a predominance that perhaps eclipses even that seen in the earlier period of suppressor T cell ascendancy. This brief review summarizes the rise and fall of 'suppressorology' and the possibility that Tregs are a modern rediscovery of suppressor T cells made convincing by more robust models for their study and better reagents for their identification and analysis.

An essential role for IL-18 in CD8 T cell-mediated suppression of IgE responses

The ability of CD8 T cells to suppress IgE responses is well established. Previously, we demonstrated that CD8 T cells inhibit IgE responses via the induction of IL-12, which promotes Th1 and suppresses Th2 responses. In this study, we show that IL-18 also plays an essential role in IgE suppression. In vitro, IL-18 synergized with IL-12 to promote Th1/T cytotoxic 1 and inhibit Th2/T cytotoxic 2 differentiation. OVA-specific TCR transgenic (OT-I) CD8 cells induced both IL-12 and IL-18 when cultured with OVA(257-264) peptide-pulsed dendritic cells. In vivo, IL-18(-/-) mice exhibited higher IgE and IgG1 levels compared with wild-type mice after immunization with OVA/alum. Furthermore, adoptive transfer of CD8 T cells from OVA-primed mice suppressed IgE responses in OVA/alum-immunized mice, but not in IL-18(-/-) mice. IgE suppression in IL-18(-/-) mice was restored if CD8 T cells were coadoptively transferred with IL-18-competent wild-type bone marrow dendritic cell progenitors, demonstrating an essential role of IL-18 in CD8 T cell-mediated suppression of IgE responses. The data suggest that CD8 T cells induce IL-18 production during a cognate interaction with APCs that synergizes with IL-12 to promote immune deviation away from the allergic phenotype. Our data identify IL-18 induction as a potentially useful target in immunotherapy of allergic disease.

Regulatory T cells--the renaissance of the suppressor T cells

Immune reactions are stringently regulated and balanced by complex interactions of stimulating and suppressing mechanisms. Dysfunctions of this sophisticated immune regulatory network can lead to a variety of diseases such as autoimmunity, allergy, cancer, and pregnancy disorders. The rediscovery of suppressor T cells a decade ago--now designated as T regulatory cells--set off a huge avalanche of research activities leading to a multitude of preclinical and clinical studies. Herein, we give a comprehensive review about this research on T regulatory cells and the relevance of this suppressive T cell population for the development of innovative immune therapeutic strategies.

CD8 T cells inhibit IgE via dendritic cell IL-12 induction that promotes Th1 T cell counter-regulation

Th1 and Th2 cells are counterinhibitory; their balance determines allergic sensitization. We show here that CD8 T cell subsets break these rules as both T cytotoxic (Tc)1 and Tc2 cells promote Th1 over Th2 immunity. Using IL-12(-/-), IFN-gamma(-/-), and OVA(257-264)-specific Valpha2Vbeta5 TCR-transgenic mice, we have identified the key steps involved. OVA-specific IFN-gamma(-/-) CD8 T cells inhibited IgE responses equivalent to wild-type CD8 T cells (up to 98% suppression), indicating that CD8 T cell-derived IFN-gamma was not required. However, OVA-specific CD8 T cells could not inhibit IgE in IFN-gamma(-/-) recipients unless reconstituted with naive, wild-type CD4 T cells, suggesting that CD4 T cell-derived IFN-gamma did play a role. Transfer of either Tc1 or Tc2 Valpha2Vbeta5 TCR-transgenic CD8 T cells inhibited IgE and OVA-specific Th2 cells while promoting OVA-specific Th1 cell responses, suggesting a potential role for a type 1 inducing cytokine such as IL-12. CD8 T cells were shown to induce IL-12 in OVA(257-264)-pulsed dendritic cells (DC) in vitro. Furthermore, CD8 T cells were unable to inhibit IgE responses in IL-12(-/-) recipients without the addition of naive, wild-type DC, thus demonstrating a pivotal role for IL-12 in this mechanism. These data reveal a mechanism of IgE regulation in which CD8 T cells induce DC IL-12 by an IFN-gamma-independent process that subsequently induces Th1 and inhibits Th2 cells. Th1 cell IFN-gamma is the final step that inhibits B cell IgE class switching. This demonstrates a novel regulatory network through which CD8 T cells inhibit allergic sensitization.

The effects of pollutants on the allergic immune response

An increase in the prevalence of allergy and allergic diseases has taken place in the industrialised countries. Allergic diseases represent a major health problem, and appear linked to affluence and modern lifestyle. In the 20th century air pollution from industrial sources largely has been replaced by diesel exhaust and other traffic pollution. Further, the indoor environment in which we spend most of our time has changed dramatically. In order to understand the contribution of pollution and other environmental changes to the development of allergy, we need to understand the biologic processes that underlie allergic immune responses. In the present paper, immune regulatory pathways that control the allergic immune response are delineated. Castor bean dust causes widespread allergic sensitisation. The investigations that made clear the importance of CD8 T cells for the regulation of IgE production were triggered by studies of castor bean allergy. A special focus is in this review placed on the regulatory role of CD8 T cells in the development of the allergic immune response.

CD8(+) T cell subsets and chronic obstructive pulmonary disease

COPD is a debilitating and progressive condition in which the airways become irreversibly obstructed and the lungs progressively damaged. Unlike asthma, we know little about the cells that initiate and drive this process. Research has shown that CD8(+) T cells are overrepresented in the lungs of patients with COPD and that they are inversely related to lung function. However, not all CD8(+) T cells are alike and subsets that make IFN-gamma but not IL-4 (Tc1), IL-4 but not IFN-gamma (Tc2) as well as those that make both (Tc0) have been described. This article focuses on the characteristics of CD8(+) T cell subsets and considers their potential contribution to chronic obstructive pulmonary disease (COPD). Kemeny DM, Vyas B, Vukmanovic-Stejic M, Thomas M, Noble A, Loh LC, O'Connor BJ. CD8(+) T cell subsets and chronic obstructive pulmonary disease.

In vivo-induced suppression of T cell proliferation: the relationship between the specificity of induction and control

We have previously shown that sc immunization of C57BL/10 (H-2b) mice with the tobacco mosaic virus protein (TMVP) or with its tryptic peptide number 8, representing residues 93-112 of TMVP, induces T cells which proliferate in vitro in response to TMVP and to peptide 8. In contrast, immunization of B10.BR (H-2k) mice either with TMVP or with peptide 8 induces T cells which respond in vitro to the homologous but not the heterologous Ag. In the present article , we report that in the B10.BR (H-2k) strain, ip prepriming with (TMVP) 7 days prior to sc immunization with peptide 8 causes a drastic reduction in the in vitro proliferative response of peptide 8-specific T cells while no such effect is seen in the congenic C57BL/10 (H-2b) strain. This suppression of T cell responsiveness can be transferred with TMVP-primed spleen cells. Moreover, deleting T cells from the transferred spleen cells abrogates the suppressive effect. In both H-2 haplotypes, ip prepriming with peptide 8 causes suppression of the proliferative T cell response induced by subsequent immunization with peptide 8. This prepriming has no effect on the response to TMVP immunization of B10.BR mice but does effect the response of C57BL/10 mice. Using various synthetic peptides to analyze the specificity of the suppression, we have determined that (1) T cells involved in the suppression of the proliferative T cell response to a single peptide determinant do not suppress the proliferative T cell response to other determinants on the protein antigen and (2) these T cells with suppressor function, and proliferating T cells which are ultimately regulated, can exhibit specificity for the same epitope. These studies suggest that there may exist fundamental differences as to how T cells which participate in suppression an proliferating T cells (which include mainly T helper cells) recognize protein antigens.

Altered immune response patterns in murine syngeneic pregnancy: presence of natural null suppressor cells in maternal spleen identifiable by monoclonal antibodies

Expression of certain autologous lymphocyte-activating antigenic determinants on the developing embryo is known to provide a stimulus for maternal anti-fetal autoproliferative responses. If left unregulated these responses could exert negative influences on the reproductive process by converting to autoaggressive forms of immune reactivity. In normal circumstances, immunological reactions of this nature are therefore likely to be under the control of pregnancy-associated immunoregulatory elements found within the maternal/fetal environment. In the present investigation we describe a naturally occurring splenic inhibitory cell type devoid of conventional T, B, and macrophage surface markers associated with syngeneic murine pregnancy that is capable of exerting potent immunosuppressive effects on an in vitro expression of fetal/newborn T cell autoreactivity, namely the autologous mixed lymphocyte reaction (AMLR). Maternal spleen cells inhibitory for AMLR were found to be highly resistant to cytotoxic pretreatment with a panel of conventional antisera directed against T cell-specific antigenic determinants. The non-T nature of the natural splenic suppressor cell was further indicated by experiments showing that purified spleen T cells had no inhibitory activity. Pregnancy spleen cell populations that were effectively depleted of macrophages retained full ability to inhibit AMLR. Maternal suppressor activity could be localized to the spleen cell population bearing receptors for the B cell-specific lectin, soybean agglutinin (SBA). A panel of monoclonal antibodies prepared against enriched populations of suppressor cells was screened and selected for specific reactivity using an ELISA against glutaraldehyde-fixed SBA+ spleen cell subpopulations from pregnant versus virgin animals. Several of the monoclonals developed against suppressor-enriched spleen cell populations from isopregnant as well as allopregnant animals were effective in reducing or eliminating suppressor cell activity following cytotoxic pretreatment in the presence of complement. The novel set of anti-suppressor monoclonal antibodies described here should prove useful in furthering the isolation and characterization of pregnancy-associated suppressor cells and in determining their relationship to natural suppressor cell populations described in other systems.

Participation of serotoninergic system in neuroimmunomodulation: intraimmune mechanisms and the pathways providing an inhibitory effect

Exogenous serotonin administration as well as its precursor 5-oxytryptophan, blockade of the ferment inactivation by MAO inhibition, impairment of the monoamine binding, in other words, all the ways of elevation of active serotonin level, result in the inhibition of the immune response. On the contrary, exclusion of the serotoninergic system by the nuclei raphe lesion and the blockade of the synthesis ferments by p-chlorphenylalanine and p-chloramphetamine stimulates it. The present analysis permits us to conclude that the nuclei raphe serotoninergic system provides an inhibitory mechanism of the immune response modulation, that is realized via the hypothalamus-hypophysis-adrenals axis. Immune response modulation by the extraimmune control system is possible only be means of the mechanisms that are present in the immunocompetent system. Investigation of the cellular basis of physiological mechanisms of serotoninergic regulation of the immune process made it possible to determine alterations in the correlation of functionally different cell populations in animals with elevated serotonin level. An inhibitory action which serotonin produces upon the immunogenesis, is based on the attenuation of suppressor cell function, an earlier than under the normal immune response development emergence of suppressor in the population of cell organs, and their longer presence, that is to some extent connected with the redistribution of cell populations in the immunocompetent organs. After serotonin administration only the antigen-nonspecific immunosuppression is activated. In evolutionary terms the mechanisms of nonspecific suppression have been formed earlier than those of specific ones (Calkins & Stutman, 1978; Mijawaki, Seki, Kubo & Tanigushi, 1979). It is quite reasonable that extraimmune modulation, and psychoneuroimmunomodulation by monoamine systems in particular, can be performed by means of this ancient antigen-nonspecific mechanism of the immune response regulation. In this case, the modulation of immunological reactivity should correspond to these endogenous and environmental influences. Thus, activation of the nonspecific suppression induced through the serotoninergic system can be considered as the universal mechanism which on the one hand completes control of the immune homeostasis and on the other may be the precondition of the development of pathological states caused by the reduction of immunological status.

I-J expression is not associated with murine chromosome 4

I-J originally mapped within the murine major histocompatibility complex (H-2) between the EB and Ea loci using intra-H-2 recombinants. Cloning of this segment of H-2 shows no DNA that can be ascribed to I-J. Various hypotheses have attempted to explain this dilemma. One hypothesis attributes a chromosome 4 locus with I-Jk expression. This hypothesis requires the AKR/J and A/WySn mouse strains to be I-Jk negative. In the present report we show that AKR/J spleen cells express I-Jk surface molecules and that both the AKR/J and A/WySn mouse strains produce functional I-Jk-bearing suppressor factors to poly(Glu50Tyr50). Our data imply that mapping of I-J-determining genes to chromosome 4 may be premature.

Regulatory mechanisms in immune responses to heterologous insulins. II. Suppressor T cell activation associated with nonresponsiveness in H-2b mice

Murine antibody responses to insulins are controlled by MHC-linked Ir genes. Although mice of the H-2b haplotype do not make antibody in response to pork insulin, we demonstrate in this communication that immunization with pork insulin stimulates radioresistant, Lyt-1+2- helper T cells that are capable of stimulating secondary antibody responses to pork insulin in vitro, but that this activity is masked by radiosensitive, Lyt-1-2+, I-J+ suppressor T cells. The suppressor T cells, present after immunization with pork insulin but not beef insulin, suppress the secondary response to pork but not beef insulin. The amino acid sequences of pork and beef insulins differ only at the A-chain loop; thus, pork insulin-specific suppressor T cells appear to recognize the A-chain loop determinant of pork insulin. The amino acid sequences of mouse and pork insulin are identical in the A-chain loop, which suggests that these suppressor T cells may be self-reactive. If this interpretation is correct, these suppressor T cells could be involved in the maintenance of self-tolerance to insulin. Nevertheless, these data clearly demonstrate that genetically determined nonresponsiveness in H-2b mice is conferred by activation of dominant, insulin-specific suppressor T cells (Ts), rather than by a defect in the stimulation of insulin-specific helper T cells (Th).

Concomitant induction and persistence of hapten-specific suppressor and helper T cells in vivo

Intravenous injection of haptenized syngeneic lymphoid cells in the mouse induced a suppression in vivo against any immunogen carrying this hapten, introduced as a second antigen. Suppression was observed against any epitope on such a haptenized immunogen, thus largely excluding cross-reactions at the level of antigen-binding or idiotypy. However, when cells from such suppressed mice were assessed in vitro, it could be shown that significant T-helper activity had been induced by the same procedure, which in vivo resulted in suppression only. Thus, concomitant induction and persistence of hapten-specific suppressor and helper T cells is a result of the present immunization protocol. Both phenomena express the conventional requirements for physical linkage between hapten and immunogen to have an impact on the antibody response against the epitopes of the carrier. It is thus likely that the observed suppression/help in the present system does function at the level of handling the intact immunogen.

Self- and allo-specific suppressor T cells evoked by intravenous injection of F protein

The liver/serum protein F appears to inactivate clones reactive towards itself in the T helper cell but not the B cell compartment. To examine the extent of self-reactivity in the T suppressor cell compartment, the well-established procedure of i.v. injecting milligram doses of the protein was used. To detect suppression, an entirely in vitro proliferation assay was devised, based on use of immunopurified F antigen. In this way T suppressor cells could be detected after activation either by allogeneic F, or (though to a lesser extent) by self-F protein. Thus the T suppressor cell compartment contains potentially self-reactive clones, and to that extent the receptor repertoire of T suppressor cells overlaps with B rather than T helper cells.

Depletion of murine anti-azobenzenearsonate plaque-forming cells by derivatized polyacrylamide beads

The depletion of secondary p-azobenzenearsonate plaque-forming cells (ABA-PFC) by affinity columns substituted with ABA was dependent on the primary dose, times elapsed after priming, and the nature of the side-arm on the columns. Thus, higher priming doses of ABA coupled to keyhole limpet haemocyanin (50-500 micrograms of ABA-KLH in complete Freund's adjuvant (CFA] favoured depletion of ABA-PFC by ABA coupled to a 6- aminocaproyltyrosine side-arm (SAC-TYR-ABA beads), whereas ABA-PFC from mice primed with 1 microgram of ABA-KLH in CFA were never depleted; this latter population were only depleted by ABA coupled to a histamine side-arm (HIST-ABA beads) 7 months after priming. These data are consistent with the notion that two specificities, HIST-ABA and TYR-ABA, appear to emerge independently, lower priming doses inducing the preferential appearance of the HIST-ABA specificity.

Inactivation of specific anti-H-2 suppressor T cells by antisera to I-J and I-C subregion products of the H-2 complex

Two antisera to Ia antigens, products of the H-2 complex I-Cd and I-JkEk subregions, respectively, have been obtained by immunization of the F1 hybrids of recombinant strains of mice. These antisera are shown to display a 50% cytotoxic effect in vitro, in the presence of complement, upon lymphocyte populations immune to the H-2-complex antigens and enriched for specific suppressor T cells (SSTC) by fractionation on a monolayer of target cells. The specificity of anti-Ia cytotoxins is shown by cross-antibody absorption with T and B cells of mice originating from the recombinant H-2 haplotypes and bearing either particular I-Cd, I-Jk and I-Ek antigens, or their combinations. Anti-I-Cd cytotoxins were found to react with both B and T cells, but at a different rate, and the anti-I-JkEk serum contains two antibody types directed to I-Ek and I-Jk products, respectively, the latter being able to react preferently with T cells. Although both antisera do inactivate the in vitro SSTC function in the presence of complement to a similar degree, the inactivating action of the anti-I-Cd serum, but not that of the anti-I-JkEk serum, occurs without complement. SSTC are shown to bear both Ia-antigens, I-J and I-C, as shown by both inactivation of the anti-suppressor effect of the antisera absorbed with spleen cells of different H-2 origin, and variation of the H-2 origin of SSTC pretreated with the intact antisera. It is suggested that these two markers, located on the same SSTC, function differently in SSTC immune to the H-2 antigens, and I-C antigen expression on the SSTC surface is presumed to be required for their interaction with the inhibited responder T cells proliferating in MLC.

Cell separation using positive immunoselective techniques

Positive immunoselection is the direct selection and recovery of cells which express a given specificity from among a heterogeneous group of contaminating cells. A variety of methods are available to effect such separations. The principles of affinity chromatography, using solid-phase matrices or cellular immunoadsorbents, are extensively used. Liquid-phase positive immunoselection can also be performed using either a fluorescence-activated cell sorter or by using 'cellular engineering' to protect a cell from an otherwise noxious environment. The enzyme catalase coupled to specific antibody has been used for this purpose and renders cells resistant to hydrogen peroxide. The various positive immunoselection techniques available are reviewed and evaluated in the following report.

Temperature-sensitive mutant of coxsackievirus B3 establishes resistance in neonatal mice that protects them during adolescence against coxsackievirus B3-induced myocarditis

Inoculation of neonatal CD-1 mice by multiple routes with an amyocarditic temperature-sensitive (ts) mutant (ts 1) derived from a myocarditic parent variant of coxsackievirus B3 (CVB3(m)) resulted in approximately half of the neonates surviving to adolescence. Challenge of the ts 1 survivors with CVB3(m) did not induce myocarditis, as assessed by histological examination of heart tissues. Virus was not detected in heart tissues of adolescent ts 1 survivors, but inoculation of these mice with CVB3(m) resulted in virus concentrations similar in titers to those found in CVB3(m)-inoculated normal adolescent mice. The ts 1 survivors did not contain detectable levels of anti-CVB3(m) neutralizing antibody, but upon challenge with CVB3(m) they produced antibody more rapidly and to higher titers than did normal CD-1 adolescents after primary inoculation with CVB3(m). Cell-mediated immunity in ts 1 survivors was compared with that of normal mice after challenge with CVB3(m). The capacity for production of migration inhibitory factor was assessed by the agarose droplet cell migration inhibition assay, using peritoneal exudate cells and a CVB3(m) cell lysate or KCl-extracted antigens from heart tissues of CVB3(m)-inoculated mice. Migration inhibitory factor activity was not detected in cultures of splenic leukocytes from ts 1 survivors of CVB3(m)-inoculated ts 1 survivors, but it was readily detected in cultures of splenic leukocytes from CVB3(m)-inoculated normal adolescent mice. The [(3)H]thymidine stimulation assay, performed with splenic lymphoid cells and purified CVB3(m) particles, revealed that lymphocytes from normal mice, whether inoculated with CVB3(m) or not, were not stimulated by CVB3(m) particle antigens, whereas lymphoid cells from a significantly higher proportion of ts 1 survivors, whether inoculated with CVB3(m) or not, responded with a stimulation index >/=2.0. The cells responding with positive stimulation were T lymphocytes. A higher proportion of normal mice and ts 1 survivors, both inoculated with CVB3(m), contained splenic cytotoxic T lymphocytes with higher reactivity against CVB3(m)-infected neonatal skin fibroblasts than against normal skin fibroblasts, as assessed by a (51)Cr release assay. The group of uninoculated ts 1 survivors present as a high proportion of individuals with cytotoxic T-lymphocyte reactivity against both uninoculated and CVB3(m)-inoculated skin fibroblasts. However, ts 1 survivors and normal mice possessed the same proportions of splenic lymphocytes carrying either allele for Lyt 1 and Lyt 2 surface markers. The results suggest two mechanisms by which ts 1 survivors exhibit resistance to CVB3(m) induction of myocarditis, namely, the rapid production of high-titered anti-CVB3(m) neutralizing antibody in response to CVB3(m) inoculation and altered cell-mediated immune responses against CVB3(m)-induced viral or novel cellular antigens. The data are compatible with the notion that an immune deviation mechanism, thought to be controlled through a mechanism requiring suppressor cell activity which inhibits macrophage activation in ts 1 survivors, protects these mice from induction of myocarditis.

Detection of antigen specific rosette formation with the FACS

Donors previously sensitized to conventional antigens PPD and KLH were evaluated for their antigen binding responses, utilizing a rosette forming technique with antigen-conjugated autologous erythrocytes. Reactivity is directly correlated with prior sensitization. Furthermore, antigen specificity is suggested by inhibition of rosette formation by prior incubation with the relevant antigen. The frequency of RFCs detected cytofluorometrically was compared with conventional fluorescent microscopy determinations. RFCs detected in this manner were identified as antibody armed monocytes by cell depletion and histochemical studies. The usefulness of the rosette forming technique for the routine evaluation of donor immunity is discussed.

H-2-controlled suppression of T cell response to lactate dehydrogenase B. Characterization of the lactate dehydrogenase B suppressor pathway

We characterized the cell types involved in the H-2-controlled suppression of T cell response to lactate dehydrogenase B (LDHB). The suppressor effector (Tse) was found to be an Lyt-1+2+, J+ cell that recognizes antigen together with Ek molecules of antigen-presenting cells (APC). To become functional, the Tse cell requires a second signal from a nonspecific, Lyt-1+2-, J+ suppressor-inducer (Tsi) cell. The Tsi-Tse interaction is not subject to any genetic restriction. The target cell of suppression is an Lyt-1+2-, J- (most likely T helper [Th]) cell that recognizes LDHB in the context of A molecules on APC. The suppression is manifested in inhibition of the antigen-specific, A-restricted proliferation of Th cells. The interaction between Tse and Th is restricted by the A region of the H-2 complex. Because this restriction is determined by the receptor of Th cells, the mechanism of Th-Tse interaction most likely involves a concomitant recognition of LDHB and A region-controlled molecules by Th cells on the surface of Tse cells.

T cell signals in tolerance

In contact sensitivity (and other forms of T cell sensitivities), T cell activation and priming of the system requires at least two signals. Signal 1 includes specific antigen and signal 2 is a nonspecific stimulus. Ordinarily, the signals are invoked in an associative manner, but they can be delivered separately. The physiocochemical nature of the antigen and the manner of host processing are critical to the delivery of signal 2. Tolerance in unprimed systems is induced by the presentation of signal 1 (antigen) in forms and by routes that do not activate signal 2. This seems to invoke suppressor mechanisms and to directly inactivate TDH cells. In primed systems where contact sensitivity is present, signals 1 and 2 boost the response. In primed systems, "off signals" (desensitization) may be provided by some anti-id antibodies, which act by stimulating suppressor mechanisms that finally work to down regulate TDH. Antigen alone (signal 1) also appears to be capable of directly down regulating TDH, but so far it has not proved a powerful tool in desensitizing primed T cells.

Cell-to-cell interaction controlled by immunoglobulin genes. Role of Thy-1-, Lyt-1+, Ig+ (B') cell in allotype-restricted antibody production

A novel lymphocyte subpopulation, designated "B' cell" because of its characteristic dual expression of Ig and Lyt-1 antigen, is described in relation to its ability to augment the in vitro secondary antibody response. The cells are found in the spleens of normal unprimed mice as well as those of athymic nude mice and represent a small of normal unprimed mice as well as those of athymic nude mice and represent a small number (2-3%) of immunoglobulin-positive cells. No other distinguishing surface markers of conventional T and B cells, such as Thy-1, Lyt-2, Ia, and ThB antigens, are detected on the B' cell. In the in vitro anti-hapten secondary antibody response, the addition of a small number of B' cells from unprimed mice to the mixture of T and B cells greatly augmented the anti-hapten antibody formation when the number of carrier-specific helper T cells was limited. This augmentation was observed only when B and B' cells shared the same set of IgVH genes. The identity of the immunoglobulin gene between T cells and B or B' cells was not necessary for optimum antibody production. The results indicate that the presence of B' cells is necessary for the induction of an optimum antibody response when helper T cells are limited. It is suggested that B' cells deliver an additional signal to the B cell network to magnify the antibody response.

Alloantigens expressed on a subset of unstimulated human T lymphocytes that generate suppressor function

Human alloantisera were tested for antibodies reacting with T-cell subpopulations. T-cell subsets were separated using the monoclonal antibodies OKT4 and OKT8. Five sera reacting with the T4-T8+ subset and two sera reacting with T4+T8- lymphocytes were identified. Serum Z. G. reacted with T4-T8+ cells from 8 of a panel of 19 donors. T cells treated with Z. G. serum and rabbit complement lost the capacity to generate suppressor cells but showed no decrease in the development of cytotoxic effector cells. ZG antigens were demonstrated by absorption also on monocytes but not on B cells. Their reactions on T cells were blocked by chicken anti-human Ia serum, but not by turkey anti-beta 2-microglobulin or by a monoclonal anti-human DR (L227). Studies in four informative families suggested that the ZG determinants are inherited in linkage with HLA. Although the similarities between ZG antigens and mouse I-J products are striking, structural studies are needed to establish their homology.

Monoclonal antibodies that recognize the product controlled by a gene in the I-J subregion of the mouse H-2 complex

The B cell hybridomas producing monoclonal antibodies (E10, D7, F4, H6, and D4) were established by the fusion of P3U1 or NS-1 murine myeloma cell lines and spleen cells of B10.A(5R) mice hyperimmunized with mitomycin C-treated B10.A(3R) spleen and thymus cells. Two types of monoclonal antibodies specific for the products controlled by a gene in the I-Jb subregion of the H-2 complex were characterized: one specific for the private type of I-Jb determinant, the other recognizing the cross-reactive determinant between the I-Jb and I-Jd products. By using these monoclonal reagents, the I-J-encoded product on the antigen-specific suppressor T cells was found to be expressed on their soluble suppressor factors. Furthermore, the I-Jb products were successfully detected not only on the T cell hybridoma with suppressor activity specific for keyhole limpet hemocyanin (KLH), but also on KLH-primed suppressor T cells enriched by antigen-coated petri dishes and concanavalin A-induced thymocyte blasts of C57BL/6 mice by complement-dependent cytotoxic assays and membrane fluorescence techniques.

Requirements for induction of specific suppressor T cells and detection of their H-2 antigen-binding receptors by fractionation on target cell monolayers

The MC-resistant specific suppressor T cells that inhibit DNA synthesis and CTL generation in MLC were induced in vivo by gamma-irradiated allogeneic lymphoid cells in a large dose. MLRs were inhibited only slightly when triggered by third-party cells, even neighbouring with the corresponding stimulators. Unlike the irradiated cells, intact allogeneic lymphoid cells induced a mixture of macrophage-like and T-cell suppressors with a pronounced non-specific component of the action. Syngeneic cells induced low active non-specific suppressors of macrophage type only. The suppression was not due to a cytotoxic effect, since specific T suppressors differed from CTL by conditions of induction and high sensitivity to gamma-irradiation and from CTL precursors by high sensitivity to CY and HC. The specific T-suppressors could be selectively removed by adherence to a macrophage monolayer of the corresponding donor. The subsequent elution of adherent lymphocytes with pronase resulted in enrichment of specific T suppressors by a factor of 30 and 2.6, as judged by reduction in the number of lymphocytes required for 50% inhibition of DNA synthesis and 33% inhibition of CTL generation, respectively. The high specificity of this enrichment is shown by using both syngeneic monolayers for fractionation and third-party stimulators in MLR for testing and by disappearance of slight non-specific suppression caused by non-fractionated suppression. Complete inactivation of the eluted suppressors with anti-Thy-1.2 and anti-T antibodies, their resistance to anti-Mls antibodies, carrageenin, and carbonyl iron, together with the data of autoradiographic study and total DNA synthesis in the population indicate that the eluted highly specific suppressors represent mainly DNA-synthesizing large and medium T lymphocytes.

Demonstration of T15 idiotype-positive effector and suppressor T cells for phosphorylcholine-specific delayed-type hypersensitivity response in CBA/N or (CBA/N X BALB/c)F1 male mice

Subcutaneous immunization of CBA/N or (CBA/N X BALB/c)F1 (NBF1) male mice, which were defective in phosphorylcholine (PC)-specific humoral antibody response, with PC-conjugated syngeneic spleen cells induced a PC-specific delayed-type hypersensitivity (DTH) response, while intravenous administration of the same cells induced PC-specific suppressor T cells for the DTH response. Treatment of PC-specific effector or suppressor T cells for the DTH response induced in NBF1 male mice with anti-T15 idiotypic antibody inactivated effector or suppressor functions of these T cells implying that PC-specific T cells in NBF1 mice expressed T15 idiotypic determinants on their surface. Enrichment of PC-specific suppressor T cells was also shown by employing anti-T15 antibody-coated dishes.

Contact sensitivity to azobenzenearsonate and its inhibition after interaction of sensitized cells with antigen-conjugated cells

Painting mice on the skin with the diazonium salt of p-arsanilic acid elicited two types of T cell activity. One was restricted by the I region of the major histocompatibility complex and was responsible for the transfer of azobenzenearsonate (ABA) sensitivity to naive mice. The other was H-2K restricted and could be demonstrated by its ability to interact specifically with ABA-coupled cells in vitro and to inhibit nonspecifically the transfer of sensitivity by cells sensitized either to ABA or to another antigen. Free antigen, or antibody directed against the cross-reactive idiotype on the anti-ABA antibodies of A/J mice, could inhibit the H-2K-restricted suppressive activity induced in the ABA immune A/J cells.

Modulation of Schistosoma mansoni egg-induced granuloma formation: I-J restriction of T cell-mediated suppression in a chronic parasitic infection

Newly formed hepatic granulomas around Schistosoma mansoni eggs become progressively smaller during the chronic (greater than or equal to 15 weeks after infection) phase of the disease. This reduction in granuloma size, termed "modulation," is known to be caused in part by a T lymphocyte that can adoptively transfer modulation to 6-week-infected mice. The present study examines a possible role for the I-J locus in regulating the suppressor T lymphocyte aspects of modulation. Adoptive transfer between congeneic B10.A(3R) and B10.A(5R) mice (differing at the I-J locus) indicated that optimal suppression is dependent upon homology at the I-J locus. In vivo treatment of chronically infected mice with microliter amounts of antiserum specific for the recipient's I-J determinant blocked modulation during chronic infection and prevented adoptive transfer of suppression to 6-week-infected mice. The in vivo regimen of anti-I-J had no effect on anti-schistosomal egg antigen titers during chronic infection. These results demonstrate an I-J restriction for suppression. It appears that the suppressor T lymphocyte circuit responsible for this aspect of modulation requires an I-J positive lymphocyte.

Antigen-specific T-cell factors

Antigen-specific T-cell factors are mediator molecules which are produced by helper and suppressor T cells and which can perform the function of those cells in an antigen-specific manner. They probably play an important part in immunoregulation. The major histocompatibility complex has a controlling influence on their structure and activity, while their antigen-recognition properties may be conferred by immunoglobulin V regions. Interest in the factors derives from three related areas of research, namely (i) the problem of T-cell recognition of antigen; (ii) the mechanisms of cellular interactions in antibody production and cell-mediated immunity; and (iii) the genetic control of immune responses. This review discusses the literature up to June 1980 on their production, structure, genetic restriction and mechanism of action.

Precursor and effector phenotypes of activated human T lymphocytes

In mice, thymus-derived lymphocytes are differentiated into functional subclasses by their cell surface antigens. The Ly 1 determinants are present on T cells with a helper function, whereas Ly 2 and Ly 3 antigens are expressed on the surface of lymphocytes with suppressor or cytotoxic functions. In man also, T-cell subsets have been identified using allo- and heteroimmune sera and, more recently, using monoclonal antibodies, which seem to identify helper and suppressor or cytotoxic subpopulations. The major histocompatibility system (MHS)-encoded Ia antigens belong to several polymorphic families of membrane associated glycoproteins originally found on B lymphocytes; however, they have also been shown to be markers for suppressor T cells in mice. Recent studies have shown that in both mouse and man, T cells activated by a mixed lymphocyte reaction or by mitogens become Ia+. Furthermore, some human T lymphoid cells, either freshly isolated from peripheral blood or after in vitro activation by lectins or alloantigens, possess suppressor properties. We report here the phenotype of a T suppressor-cell subpopulation which was induced in long-term culture of lymphoid cells after activation with phytohaemagglutinin (PHA). Our results suggest that a subset of T cells was progressively expanded over a period of 8 days in culture and that, with the expression on the surface of these cells of 'Ia-like' antigens, they acquired the capacity to suppress the proliferative response of syngeneic or allogeneic lymphocytes to alloantigens or mitogens.