Antiidiotypes against anti-H-2 monoclonal antibodies. V. In vivo antiidiotype treatment induces idiotype-specific helper T cells

Mice have been treated in vivo with xenogeneic antiidiotypes prepared against a murine monoclonal anti-H-2Kk antibody, 11-4.1. B cell immune responses have been found to be altered by such treatment as evidenced by a modification in the idiotypic repertoire of the humoral response to H-2 antigens. Transfer of purified T cells into nude mice before anti-idiotype treatment showed that T cells are involved in the induction of idiotope-bearing antibodies by xenogeneic antiidiotype. Studies using bone marrow chimeras indicate that the environment in which either T or B cells mature does not appear to alter VH region genetic control of induction of antiidiotype-induced molecules. By adoptive transfer studies, T cells from antiidiotype-treated mice were found capable of modifying the idiotypic repertoire of B cells subsequently exposed to antigen even when the T cells were obtained from antiidiotype-primed mice of inappropriate allotype. Although it still must be determined whether idiotypic or antiidiotypic T cells are involved in such B cell idiotype regulation, these results indicate that some T cell functions are altered by xenogeneic antiidiotypes prepared against B cell products and suggest that T cell immunity to major histocompatibility complex antigens may also be affected by such reagents.     

The in vivo regulation of splenic T cell population by the prostaglandin-mediated system

The effects of prostaglandins (PGs) on splenic T cell population, the generation of Con A-induced suppressor T cells, and antibody response to sheep erythrocytes were examined in mice in which the in vivo level of PG was regulated by indomethacin (INDO), an inhibitor of PG-synthesis, and exogenous PGE2. Inhibition of PG-synthesis enlarged the T cell population in the spleen and such an enlargement was due to an increase in Lyt-1+2+ and Lyt-1-2+ subsets. In this group, the induction of suppressor T cells was augmented, while the antibody response was suppressed. Elevation of the PG-level scarcely affected the size of the whole T cell population in the spleen but slightly increased a Lyt-1+2- subset. The production of suppressor T cells was disturbed, and the antibody response was augmented in this T cell population. Experiments using anti-Lyt antibody plus complement showed that Lyt-1+2+ subsets exhibited these distinctive activities between PG-decreased and PG-increased mice. A Lyt-1+2+ subset from mice with a high PG-level may be in an advanced stage of maturation compared with that from mice with a low PG-level under the promoting effect of PG on T cell differentiation. In vivo regulation of the PG-level appears to play an important role in the regulation of the T cell population and immune response.     

Mitogen-reactive B cell subpopulations selectively express different sets of V regions

The experiments presented here were designed to investigate whether the idiotypic repertoire is equally distributed among B cells subpopulations as defined by mitogen reactivity. To this end we used lipopolysaccharides (LPS) and Nocardia delipidated cell mitogens (NDCM), which are two mitogens that have been described to act on different B cell subsets. The repertoire can be defined in quantitative terms as the frequency of B cells that are precursors for clones secreting immunoglobulin with a given specificity or with a determinate idiotype. We determined, therefore, the absolute frequency of LPS- and NDCM-sensitive B lymphocytes secreting immunoglobulin molecules that bear three idiotopes originally found on a monoclonal anti-beta galactosidase antibody. Because the frequencies of B cells carrying one of these idiotypes are dramatically different in the LPS- and NDCM- sensitive B cells subsets, we conclude that the idiotypic repertoire is not randomly distributed among mitogen-reactive B cell subpopulations.     

Regulatory idiotopes. Induction of idiotype-recognizing helper T cells by free light and heavy chains

Previously, we have demonstrated the induction of T helper cells that recognize idiotype by antigen (19), idiotype (20), and antiidiotype (12). The T cell population has been characterized and found to recognize both the T15 and M167 myeloma proteins, which share PC binding specificity but differ in idiotypic specificities. In the present work, we used isolated heavy and light chains of T15 and M167 to generate T helper cells, and examined the response to trinitrophenyl (TNP)-T15 and TNP-M167. We found that the heavy chains induced a dose- dependent response to TNP-T15 and TNP-M167, while the light chain priming was ineffective. When isolated chains of a monoclonal anti-T15 antibody (F6-3) were used to induce idiotype-recognizing T cells, only the F6-3 light chains generated T cell help for TNP-T15 and TNP-M167. Evidently, the idiotypic determinant that is recognized by the T cells is not dependent upon the conformation of combined heavy and light chains. These data show that the Th2 helper cells for the T15/M167 idiotopes are induced by free heavy chains of T15 and M167; the Th1 T cells that interact with the Th2 population, of T15 and M167; the Th1 T cells that interact with the Th2 population, however, can be triggered by free light chains of an antiidiotypic hybridoma antibody. These provocative findings suggest a new model for the T helper cell network.     

Antigen- and receptor-driven regulatory mechanisms. IV. Idiotype-bearing I-J+ suppressor T cell factors induce second-order suppressor T cells which express anti-idiotypic receptors

Administration of azobenzenearsonate (ABA)-coupled syngeneic spleen cells intravenously to A/J mice leads to the generation of suppressor T cells (Ts1) which exhibit specific binding to ABA-bovine serum albumin (BSA)-coated dishes. These Ts1 share idiotypic determinants with the major cross-reactive idiotype (CRI) of the anti-ABA antibodies of A/J mice, and also produce a soluble suppressor factor (TsF) bearing CRI and I-J subregion-coded determinants. Injection of this TsF into naive A/J mice elicits a second set of specific suppressor cells (Ts2) which are not lysed by anti-CRI antibody plus C, and which do not bind to ABA- BSA-coated dishes. However, in contrast with Ts1, these Ts2 do bind to plates bearing CRI+ anti-ABA immunoglobulin. Thus, Ts2 exhibit anti- idiotypic specificity. These data indicate that antigen elicits the production of a soluble T cell product bearing both variable portion of the Ig heavy chain (VH) and I-J subregion-coded determinants which serves to communicate between T cell subsets to establish an idiotype- anti-idiotype regulatory pathway.     

Antibodies to membrane structures that distinguish suppressor/cytotoxic and helper T lymphocyte subpopulations block the mixed leukocyte reaction in man

Two major subsets of human T lymphocytes that are functionally analogous to the mouse Lyt-2+ and Lyt-2- subsets have been defined by their expression of two thymus-dependent membrane antigens, Leu-2 and Leu-3. Leu-2+,3- cells have suppressor/cytotoxic functions and Leu-2- ,3+ cells have helper functions. These studies were designed to determine the effects of adding IgG1 monoclonal anti-Leu-2 and anti-Leu- 3 antibodies to the mixed leukocyte reaction (MLR). At high concentrations, each antibody partially inhibited the proliferative response of unseparated T cells and abolished the response of the isolated subset having the appropriate phenotype. An IgG1 monoclonal antibody to HLA-A2 and an IgG2a antibody to Leu-1, a pan-T antigen, failed to inhibited the MLR. These results suggest that the Leu-2 and Leu-3 antigens may have a direct role in the mechanism whereby T cells recognize and respond to alloantigen.     

Essential role for CD103 in the T cell-mediated regulation of experimental colitis

The integrin CD103 is highly expressed at mucosal sites, but its role in mucosal immune regulation remains poorly understood. We have analyzed the functional role of CD103 in intestinal immune regulation using the T cell transfer model of colitis. Our results show no mandatory role for CD103 expression on T cells for either the development or CD4+CD25+ regulatory T (T reg) cell-mediated control of colitis. However, wild-type CD4+CD25+ T cells were unable to prevent colitis in immune-deficient recipients lacking CD103, demonstrating a nonredundant functional role for CD103 on host cells in T reg cell-mediated intestinal immune regulation. Non-T cell expression of CD103 is restricted primarily to CD11c(high)MHC class II(high) dendritic cells (DCs). This DC population is present at a high frequency in the gut-associated lymphoid tissue and appears to mediate a distinct functional role. Thus, CD103+ DCs, but not their CD103- counterparts, promoted expression of the gut-homing receptor CCR9 on T cells. Conversely, CD103- DCs promoted the differentiation of IFN-gamma-producing T cells. Collectively, these data suggest that CD103+ and CD103- DCs represent functionally distinct subsets and that CD103 expression on DCs influences the balance between effector and regulatory T cell activity in the intestine.     

Both rat and mouse T cell receptors specific for the encephalitogenic determinant of myelin basic protein use similar V alpha and V beta chain genes even though the major histocompatibility complex and encephalitogenic determinants being recognized are different

Prospects for specific immune intervention in T cell-mediated autoimmune disease via anti-idiotypic regulation depend on the degree of diversity of the responder cell antigen receptor repertoire. A highly heterogenous response against self epitopes offers little chance for such regulation. We report here that the Lewis rat autoimmune disease experimental allergic encephalomyelitis, generally considered to be a model of human multiple sclerosis, is caused by T cells that use a limited set of TCR V genes. We have cloned the rat TCR alpha and beta chain cDNAs from the Lewis rat x mouse T cell hybridoma 510, which retains the rat specificity for the encephalitogenic determinant of myelin basic protein (MBP). Using Northern blot analysis of T cell RNA with the cloned V region probes, we have found a specific, and near perfect, correlation between expression of TCR message hybridizing to the V alpha 510 and VB510 probes and specificity for the encephalitogenic determinant of MBP in both T cell hybridomas and encephalitogenic T cell clones. This restricted V gene usage provides a basis for observed idiotypic regulation of auto-reactive T cells, and possible therapy for autoimmune disease. A curious and unexplained observation is that the Lewis rat V alpha/V beta combination that dominates the encephalitogenic response to the 68-88 peptide of MBP is precisely the same V alpha/V beta combination used by the B10.PL mouse response to the encephalitogenic response to the 1-9 peptide of MBP.     

T lymphocyte-mediated suppression of myeloma function in vitro. III. Regulation of antibody production in hybrid myeloma cells by T lymphocytes

To investigate the mechanisms by which T lymphocytes regulate myeloma function in vitro, the effects of regulatory T cells on antibody secretion by a hybrid myeloma cell line were examined. Suppressor T cells (Ts) specific for idiotypic determinants on M315 (IgA, lambda 2 anti-2,4-dinitrophenol and anti-2,4,6-trinitrophenol [TNP]) and MPC 11 (IgG2b, kappa) myeloma proteins inhibit antibody secretion by the appropriate parental myeloma cells. When cocultured with a hybrid cell line derived by fusion of MOPC 315 and MPC 11 myelomas, the idiotype-reactive Ts inhibit secretion of only the immunoglobulin (Ig) bearing the relevant idiotype. In contrast, syngeneic TNP-reactive cytolytic T lymphocytes (CTL) inhibit antibody secretion by TNP-binding MOPC 315 cells but not by MPC 11 cells in the presence of soluble TNP-keyhole limpet hemocyanin (KLH), and this inhibition probably represents a prelytic effect of the CTL. Such TNP-reactive CTL, in the presence of TNP-KLH, inhibit both IgA and IgG secretion by the MOPC 315-MPC 11 hybrid, which is consistent with a prelytic effect. Thus, myeloma hybrids are a useful tool for investigating the effector function of regulatory T cells. These results are discussed with reference to the mechanisms of action of regulatory T cells and their relevance to modulation of physiologic humoral immune responses.     

An insight into molecular mechanisms of human T helper cell differentiation

Selective activation of T helper (Th) cell subsets plays an important role in immune response to pathogens as well as in the pathogenesis of human allergy and inflammatory diseases. Th1 cells along with the recently discovered Th17 cells play a role in the pathogenesis of autoimmune diseases. Th2 cytokines lead to series of inflammatory processes characteristic for asthma and other atopic diseases. To understand the pathogenesis of immune-mediated diseases it is crucial to dissect pathways and regulatory networks leading to the development of distinct Th subsets. Such knowledge may lead to better strategies for developing diagnostics and therapies for these diseases. The differentiation of Th1, Th2, and Th17 effector cells is driven by signals originating from T cell and costimulatory receptors as well as cytokines in the surroundings of activated naive T helper cells. There are several proteins involved in the regulation of this differentiation process. Most of the data on T helper cell differentiation have been acquired using mouse. In this review, we have summarized what is known about human T helper differentiation. In addition, selected differences between human and mouse will be discussed.     

Cytotoxic T cells both produce and respond to interleukin 2

Interleukin 2 (IL-2) is a T cell-derived lymphokine that serves as a cofactor for the in vitro response of T lymphocytes to antigen and plays an important role in regulating the growth and/or differentiation of these cells (1, 2). It has been postulated (2, 3) that IL-2 is produced by a discrete regulatory T cell subset, with its effects being exerted on a second, functionally distinct subpopulation of T cells. Cytotoxic T cells have been included in the IL-2-responsive subset (3). Several models of immune regulation have further assumed that the T lymphocyte pool is divided into a complex array of genetically preprogrammed T cell subtypes, each performing a specific regulatory or effector function (4, 5). However, recent results from several laboratories (6-8) have failed to support such a strict functional subdivision of the T cell pool. The availability of highly purified mouse IL-2 (1) prompted us to reevaluate the distinction, if any, between IL-2-producing and IL-2- responsive T cells. For this purpose, we resorted to a cell-cloning procedure using activated T lymphocytes that were maintained only for short periods in culture. T cell clones were tested for cytotoxic activity, responsiveness to IL-2, and for the capacity to produce IL-2 after appropriate stimulation. We found no evidence for the existence of a major functional subdivision involving these parameters among alloantigen-activated T cells: the majority of clones analyzed could perform all three functions.     

CD4+ follicular regulatory T cells optimize the influenza virus–specific B cell response

CD4⁺ follicular regulatory T (Tfr) cells control B cell responses through the modulation of follicular helper T (Tfh) cells and germinal center development while suppressing autoreactivity; however, their role in the regulation of productive germinal center B cell responses and humoral memory is incompletely defined. We show that Tfr cells promote antigen-specific germinal center B cell responses upon influenza virus infection. Following viral challenge, we found that Tfr cells are necessary for robust generation of virus-specific, long-lived plasma cells, antibody production against both hemagglutinin (HA) and neuraminidase (NA), the two major influenza virus glycoproteins, and appropriate regulation of the BCR repertoire. To further investigate the functional relevance of Tfr cells during viral challenge, we used a sequential immunization model with repeated exposure of antigenically partially conserved strains of influenza viruses, revealing that Tfr cells promote recall antibody responses against the conserved HA stalk region. Thus, Tfr cells promote antigen-specific B cell responses and are essential for the development of long-term humoral memory.     

An integrated view of suppressor T cell subsets in immunoregulation

The immune system evolved to protect organisms from a virtually infinite variety of disease-causing agents but to avoid harmful responses to self. Because immune protective mechanisms include the elaboration of potent inflammatory molecules, antibodies, and killer cell activation--which together can not only destroy invading microorganisms, pathogenic autoreactive cells, and tumors, but also mortally injure normal cells--the immune system is inherently a "double-edged sword" and must be tightly regulated. Immune response regulation includes homeostatic mechanisms intrinsic to the activation and differentiation of antigen-triggered immunocompetent cells and extrinsic mechanisms mediated by suppressor cells. This review series will focus on recent advances indicating that distinct subsets of regulatory CD4+ and CD8+ T cells as well as NK T cells control the outgrowth of potentially pathogenic antigen-reactive T cells and will highlight the evidence that these suppressor T cells may play potentially important clinical roles in preventing and treating immune-mediated disease. Here we provide a historical overview of suppressor cells and the experimental basis for the existence of functionally and phenotypically distinct suppressor subsets. Finally, we will speculate on how the distinct suppressor cell subsets may function in concert to regulate immune responses.     

Anti-phosphorylcholine antibodies of the T15 idiotype are optimally protective against Streptococcus pneumoniae

In the mouse, most anti-PC antibody is found in one of the three murine anti-PC idiotype families: T15, M603, or M511. The antibodies within each of these idiotypic families have characteristic fine specificities for phosphorylcholine (PC)-analogues. In this paper we compare the ability of hybridoma IgM anti-PC antibodies of the three idiotype families to protect mice from fatal infection with S. pneumoniae. Antibody bearing the T15 idiotype was approximately 8 times as effective as antibody with the M603 idiotype and approximately 30 times as protective as antibody with the M511 idiotype. Reports by others have shown that the heavy chains of virtually all mouse anti-PC antibodies are produced by translocation of a single variable region gene and that the direct translation of this gene (in the absence of somatic mutations) results in heavy chains characteristic of the T15 idiotype. Thus, our findings suggest that the T15 germ line heavy chain variable region gene may have been selected through evolution to code for antibody binding PC-containing pathogens such as S. pneumoniae. Our observations may also explain the existence of regulatory mechanisms that result in maintenance of T15 idiotype expression in murine anti-PC immune responses.     

CD45RC Isoform Expression Identifies Functionally Distinct T Cell Subsets Differentially Distributed between Healthy Individuals and AAV Patients

In animal models of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), the proportion of CD45RC T cell subsets is important for disease susceptibility. Their human counterparts are, however, functionally ill defined. In this report, we studied their distribution in healthy controls (HC), AAV patients and in Systemic lupus erythematous (SLE) patients as disease controls. We showed that CD45RC expression level on human CD4 and CD8 T cells identifies subsets that are highly variable among individuals. Interestingly, AAV patients exhibit an increased proportion of CD45RC^low CD4 T cells as compared to HC and SLE patients. This increase is stable over time and independent of AAV subtype, ANCA specificity, disease duration, or number of relapses. We also analyzed the cytokine profile of purified CD4 and CD8 CD45RC T cell subsets from HC, after stimulation with anti-CD3 and anti-CD28 mAbs. The CD45RC subsets exhibit different cytokine profiles. Type-1 cytokines (IL-2, IFN-γ and TNF-α) were produced by all CD45RC T cell subsets, while the production of IL-17, type-2 (IL-4, IL-5) and regulatory (IL-10) cytokines was restricted to the CD45RC^low subset. In conclusion, we have shown that CD45RC expression divides human T cells in functionally distinct subsets that are imbalanced in AAV. Since this imbalance is stable over time and independent of several disease parameters, we hypothesize that this is a pre-existing immune abnormality involved in the etiology of AAV.     

Activation of antigen-specific suppressor T cells by B cells from mice immunized with type III pneumococcal polysaccharide

The transfer of B lymphocytes from mice immunized with type III pneumococcal polysaccharide (SSS-III) results in antigen-specific suppression of the antibody response of recipients immunized with SSS-III. Such suppression shares many features associated with low-dose paralysis, a phenomenon mediated by suppressor T cells; it reaches maximal levels 3 d after the transfer of viable or irradiated immune B cells and can be eliminated by the depletion of SSS-III-binding cells from spleen cell suspensions before transfer. In a two-step cell transfer experiment, purified T lymphocytes, isolated from recipients previously given immune B cells, caused suppression upon transfer to other mice immunized with SSS-III. Also, B-cell-induced suppression could be abrogated in a competitive manner by the infusion of amplifier T lymphocytes, as was previously demonstrated in the case of low-dose paralysis. These findings suggest that B cell surface components, presumably the idiotypic determinants of cell-associated antibody specific for SSS-III, are instrumental in activating suppressor T cells involved in regulating the magnitude of the antibody response to SSS-III.     

Elicitation of the prausnitz-kustner reaction by antiidiotypic antibodies.

Rabbit antiidiotypic IgG directed against IgG F(ab')2 anti-tetanus toxoid (TT) antibodies ("idiotype") elicited a Prausnitz-Kustner reaction in normal skin sites sensitized 48 h earlier with the serum of the idiotype donor that contained IgE anti-TT antibodies. The serum moiety that caused the sensitization was heat sensitive (56 degrees C, 1 h), and was specifically removed by passage over immunosorbents containing rabbit antihuman IgE or TT antigen. The data obtained indicate that human IgG and IgE antibodies share idiotypic determinants and raise the possibility that idiotypic interactions may play a role in the regulation of the IgE antibody response in man.     

Selective suppression of the major idiotypic component of an antihapten response by soluble T cell-derived factors with idiotypic or anti- idiotypic receptors

Evidence is presented for the selective suppression of the major idiotypic component of the humoral response to the phenylarsonate hapten by soluble factors derived from T cells (TsF). The existence of TsF with anti-idiotypic receptors was also demonstrated. It was found that TsF with idiotypic and anti-idiotypic receptors coexist in cultures of spleen cells prepared from idiotypically suppressed, hyperimmunized mice. By gel filtration the molecular weight of each factor was found to be 50,000-100,000. Each is sensitive to trypsin and is bound to a column containing anti-H-2a antibodies. Evidence is discussed which suggests the possibility of mutual stimulation of suppressor T cells with idiotypic and anti-idiotypic receptors.     

The injection of deaggregated gamma globulins in adult mice induces antigen-specific unresponsiveness of T helper type 1 but not type 2 lymphocytes.

Injection of adult mice with high doses of monomeric human gamma globulins (dHGG) has been previously shown to produce a state of peripheral tolerance in both B and T cells. To gain insight into the mechanism of induction and maintenance of adult tolerance in this model, we have analyzed the pattern of lymphokines produced by control and tolerant animals in response to the tolerogen. The data presented indicate that HGG-specific, interleukin 2 (IL-2)- and interferon gamma (IFN-gamma)-producing T cells (thus referred to as T helper type 1 [Th1] cells) are rendered unresponsive after in vivo administration of soluble HGG. In contrast, antigenic stimulation of T cells isolated from tolerant adult mice leads to increased production of IL-4 in vitro. In vivo challenge of dHGG-treated adult animals with hapten-coupled HGG (p-azophenylarsonate [ARS]-HGG) induced a significant ARS-specific antibody response, suggesting that tolerance induction in this model does not completely abrogate tolerogen-specific Th activity in vivo. In agreement with the in vitro data, hapten-specific antibody response of tolerant animals is characterized by a selective deficiency in the IFN-gamma-dependent IgG2a subclass. Injection of immunogenic forms of HGG into tolerant animals also produced an IL-4-dependent increase in total serum IgE levels, indicative of an increased activity of HGG-specific Th2 cells in these animals. The finding that tolerance induction differentially affects Th subpopulations suggests that crossregulation among lymphocyte subsets may play a role in the induction and/or maintenance of acquired tolerance in adults.     

Immunoregulatory studies in patients with IgA nephropathy

Numerous studies have evaluated T cell subsets and in vitro IgA synthesis in patients with IgA nephropathy. These reports have resulted in the hypothesis that defective regulation of IgA synthesis is important in the pathogenesis of IgA nephropathy. Baseline immunologic measurements were performed in a clinically well characterized group of 19 pediatric and 13 adult (greater than or equal to 18 years) patients with no macrohematuria or intercurrent infection at the time of study. Mean percentages of OKT3 and OKT4 subsets were significantly decreased for the patients as compared to healthy adult controls. Mean T4:T8 ratios were similar for control and patient groups although 7 patients had T4:T8 ratios greater than 2 SD above the control mean. Unstimulated and pokeweed mitogen stimulated in vitro IgA synthesis was similar for patients and controls. During six episodes of macrohematuria in five patients no significant changes occurred for T cell subset percentages, while mean T4:T8 ratios decreased from baseline. Mean serum concentration of IgA increased during these episodes, although in vitro IgA synthesis remained normal. Our data fail to demonstrate a consistent immunoregulatory abnormality for patients with IgA nephropathy.