Cellular and genetic control of antibody responses in vitro. III. Immune response gene regulation of accessory cell function

Allorecognition of HLA-DR and -DQ transfectants by human CD45RA and CD45R0 CD4 T cells: repertoire analysis and activation requirements

We have investigated the requirements for allogeneic stimulation of human CD4 T cells using HLA class II products expressed on various cellular backgrounds. Human (class II-negative RJ2.2.5 mutant) B cell lines transfected with HLA-DR or -DQ cDNA clones were efficient stimulators for highly purified CD4 T cells. HLA-DR-transfected mouse L cells or IFN-gamma-induced human fibroblasts, although able to function as accessory cells for T cell responses to the mitogen PHA, failed to stimulate strong T cell alloresponses. On the basis of these observations, we have employed class II transfectants to address the following questions: (a) do CD45RA and CD45R0 subpopulations differ in their allogeneic activation requirements, (b) are these subpopulations skewed in their recognition of HLA-DQ vs. HLA-DR in a manner which might support the concept that CD45RA T cells are involved in HLA-DQ-restricted suppressor inducer functions and (c) by using transfectants expressing individual HLA-DR or -DQ heterodimers in combination with limiting dilution analysis, can one for the first time obtain estimates of precursor frequencies for allogeneic cells recognizing each of these class II isotypes? Our results show that CD45RA and CD45R0 T cells respond comparably to optimal numbers of stimulator cells. However, when CD45RA and CD45R0 T cell populations depleted of endogenous accessory cells were cultured with limiting numbers of stimulator cells, CD45R0 cells generally responded more strongly, consistent with the elevated levels of various adhesion molecules known to be expressed by this population. Further, we found a similar representation of responses to HLA-DR and -DQ antigens among populations expressing CD45RA and CD45R0 isoforms. Finally, the precursor frequencies of allogeneic CD4 T cells responding to particular HLA-DR alleles were higher than to -DQ, but only by a factor of about 1.6, indicating that HLA-DQ recognition may occur more frequently than implied from previous antibody blocking studies.

Major histocompatibility complex regulation of the class of the immune response: the H-2d haplotype determines poor interferon-gamma response to several antigens

The lymph node cells of CBA (H-2k), but not BALB/c (H-2d) mice, release interferon (IFN)-gamma into the supernatant when immunized with picryl chloride epicutaneously and then exposed to antigen (haptenized cells) in vitro 4 days later. The failure in IFN-gamma production maps to the major histocompatibility complex (MHC; H-2d) in the congenic BALB/c, BALB/k and BALB/b mice. The evidence that this is an MHC regulation of the class of response to a range of antigens and not a classical Ir gene effect is (a) the difference is seen with several antigens including picryl chloride, "oxazolone" and purified protein derivative of tuberculin and (b) BALB/c mice, which fail to produce IFN-gamma, show excellent contact sensitivity to picryl chloride. It was also found that the crosses between responder and nonresponder strains (CBA x BALB/c)F1 respond to antigen on responder cell but not on nonresponder cells. This influence of MHC on the class of the immune response is a possible basis for some of the associations of MHC with disease.

The molecular basis of MHC-restricted antigen recognition by T cells

In order to determine the contribution of the clonotypic T cell receptor (Ti) alpha beta heterodimer to the antigen/MHC specificity of mature T cells, we have transfected cloned Ti alpha and/or beta genes into either human or mouse T cells, and analyzed the transfectants for Ti-T3 expression and responses to antigen and Ia molecules. Our analysis establishes that a single receptor structure (the Ti alpha beta heterodimer) is necessary and sufficient to define the dual specificity of T cell antigen recognition and suggests that in at least certain instances Ti beta chains play a predominant role in MHC restriction specificity, raising the possibility of a "one receptor, two sites" model of T cell recognition.

Inhibition of lymphocyte proliferation by free fatty acids. III. Modulation of thymus-dependent immune responses

Free fatty acids (FFA) were tested for their effects on in vitro thymus-dependent (TD) and thymus-independent (TI) immune responses. Murine T cells proliferating in one-way mixed leucocyte reactions (MLR) were extremely sensitive to inhibition by exogenous stearic acid (18:0) but were only moderately affected by oleic acid (18:1). T-cell proliferation was suppressed when 18:0 was added as late as 44 hr after allogeneic stimulation, but sensitivity to 18:1 was limited to the first 30 hr of culture. The inhibitory effects of 18:0, but not 18:1 were potentiated by concomitant T-cell activation and under such conditions the effects of 18:0 were irreversible within 5 hr. The two fatty acids were additionally tested for their effects on the anti-hapten antibody-secreting cell responses to TD and TI antigens. Both 18:0 and 18:1 inhibited the primary antibody response elicited by a TD antigen (TNP-KLH) but neither fatty acid significantly affected the primary antibody response to a TI antigen (TNP-LPS). Following in vivo immunization with TNP-KLH, isolated spleen cells were challenged with the same antigen in vitro in the presence of FFA. Whereas 18:1 had little effect on the secondary immune response, the addition of 18:0 led to a 3-4-fold increase in the number of anti-TNP plaque forming cells. Further studies showed that TNP-KLH-induced T cell proliferation was potently inhibited by 18:0 but 18:1 had no effect. These results suggest that an inhibition of T-cell proliferation is the primary way in which 18:0 modulates TD immune responses in vitro. By contrast, 18:1 appears to inhibit primary antibody responses and MLR via alternative mechanisms.

The role of Langerhans cells in antigen presentation

Epidermal Langerhans cells are dendritic bone marrow-derived cells which synthesize and express Ia antigens. During the past decade, in vitro studies have demonstrated that they play a critical role in the induction of many types of T-cell responses. Specifically, Langerhans cells are effective antigen-presenting cells in allogeneic and antigen specific proliferative and cytotoxic T-cell responses. This paper reviews these functions and suggests areas of future investigations into the mechanisms involved in T-cell activation by Langerhans cells.

T cells discriminate between Ia antigens expressed on allogeneic accessory cells and B cells: a potential function for carbohydrate side chains on Ia molecules

Previous studies have shown that the peptides obtained from accessory cell and B-cell Ia molecules are identical but that the alpha chains of B-cell Ia molecules are more extensively sialylated than those of accessory cells. The present studies were designed to determine whether this glycosylation difference can account for the functional difference in the capacity of the two cell types to activate alloreactive T cells. The experimental data show that normal resting B cells lack the capacity to induce DNA synthesis or differentiation in alloreactive T cells. T cells do recognize polymorphisms in B-cell Ia molecules, however, because they can be specifically primed for a subsequent proliferative stimulus of the same haplotype. The mitogenic signal for T cells is delivered by either allogeneic accessory cells or neuraminidase-treated B cells. Therefore, the T-cell receptor(s) may contain a site specific for the nonpolymorphic asialocarbohydrate moiety on the alpha chains of accessory cell Ia molecules.

The capacity of murine alveolar macrophages to stimulate antigen-dependent T-lymphocyte activation and proliferation

To define the antigen-presenting capacity of alveolar macrophages (AM phi), their ability to activate antigen-specific T cells was determined. It was found that AM phi s are at least as potent as spleen cells at presenting alloantigen or soluble protein antigen plus I-region determinant to cloned T-cell hybridomas. Activation of those hybridomas, shown by interleukin 2 (IL-2) secretion, further indicated the presence on AM phi s of functional products of the I-A and I-E subregions. In addition, it was found that AM phi s are at least as potent as spleen cells and peritoneal macrophages at inducing, in a restricted fashion, specific proliferation of primed, propagated lymph node T cells. AM phi s are thus potent accessory cells in vitro, whose in vivo significance in this capacity remains to be defined.

Elicitation and detection of in vitro H-2-linked Ir gene regulated antibody responses to poly(LTyr, Glu)-poly(DLAla)--poly(LLys)

A microculture system is described in which secreted antibody responses to the synthetic polypeptide (T,G)-A--L were obtained in vitro. Responses were highly reproducible, antigen-dependent, antigen-specific, and under H-2-linked Ir gene control. Critical elements in the system include the schedule of in vivo antigen-priming, removal of the stimulating antigen after 3 days of culture, and a sensitive detection system (double-antibody ELISA). This system should be useful in the analysis of the mechanism of action of Ir genes as well as the mechanisms by which anti-idiotype antibodies modulate immune responses.

Distinct helper activities control growth or maturation of B lymphocytes

A clone (C-11) of C3H/HeJ Lyt-1+2-T cells with specificity for "minor" antigens of C3H/Tif has been isolated which, in contrast to other similarly derived clones, did not activate polyclonal plaque-forming cell (PFC) responses in T cell-depleted "target" spleen cells. This clone, however, showed unaltered proliferative responses to the naturally occurring antigen(s) on presenting cells, and strongly synergized with regular helper clones in the induction of PFC responses. Further analysis demonstrated that C-11 cells are competent to stimulate extensive "target" B cell proliferation, but lack the ability to produce (or participate in the production of) maturation factors for activated B cells. Thus, the defective PFC responses could be fully reconstituted with supernatants from regular clones stimulated with antigen, but not by supernatants prepared from the C-11 cells themselves. While it is not clear whether this clone represents a normal helper T cell subpopulation or a variant that has lost maturation-factor production, these results demonstrate that distinct factors control growth and maturation in T cell-dependent B lymphocyte responses.

Major histocompatibility complex-restricted self-recognition in responses to trinitrophenyl-ficoll. Adaptive differentiation and self-recognition by B cells

The present study has examined the possibility of TNP-Ficoll-responsive B cells recognize the MHC determinants expressed by the accessory cells with which they interact for the generation of T cell-independent responses to "high" concentrations (10(-2) micrograms/ml) of TNP-Ficoll. In experiments with B cells from normal mice, it was found that MHC homology between the TNP-Ficoll-responsive B cells and accessory cells was not required. Nevertheless, TNP-Ficoll-responsive B cells from both fully allogeneic (A leads to B) and F1 leads to parent radiation bone marrow chimeras were triggered by accessory cells expressing host-type, but not uniquely donor-type, MHC determinants. The MHC gene products responsible for this apparent B cell-accessory restriction were encoded in the left side, i.e., the K and/or I-A region, of H-2. Such genetic restrictions were shown not to be imposed by the residual T cells contaminating the chimeric B cell populations because T cell reconstitution experiments using "unrestricted" F1 T cells from normal mice did not fully overcome the marked preference of the chimeric B cells for accessory cells expressing appropriate (host-type) MHC determinants. To directly determine whether TNP-Ficoll-responsive B cells from fully allogeneic chimeras are unable to recognize and cooperate with syngeneic strain A accessory cells, unfractionated spleen cells from A leads to B chimeras are co-cultured with unfractionated spleen cells from essentially syngeneic normal strain A mice. In such co-cultures, all the accessory cells express strain A MHC determinants, and all T cell requirements would be fulfilled by the T cells present in the normal strain A spleen cell population. After stimulation of the co-cultures with TNP-Ficoll, it was found that virtually all the PFC that had been generated in the co-cultures were derived from the normal B cell population, and essentially none were derived from the chimeric A leads to B B cell population. The failure of the chimeric B cells to be activated in such co-cultures was specifically due to their maturation in a fully allogeneic host environment because TNP-Ficoll-responsive B cells from A leads to (A X B) F1 chimeric mice were successfully triggered in co-cultures with normal spleen cells. These experiments demonstrated that the co-culture conditions did fulfill the MHC restriction requirements for activating TNP-Ficoll-responsive strain A B cells that had matured in a syngeneic or semi-syngeneic differentiation environment, but did not fulfill the MHC restriction requirements for activating TNP-Ficoll-responsive strain A B cells that had matured in a fully allogeneic differentiation environment. Taken together, these results demonstrate that (a) TNP-Ficoll-responsive B cells recognize the MHC determinants expressed by accessory cells, and (b) their MHC specificity is influenced by the MHC haplotype of the host environment in which the B cells had differentiated.

Functional helper activity of monoclonal T cell populations: antigen-specific and H-2 restricted cloned T cells provide help for in vitro antibody responses to trinitrophenyl-poly(LTyr,Glu)-poly(DLAla)--poly(LLys)

The ability of long-term cultured and monoclonal T cell populations to provide antigen-specific help was assessed in a system of Ir gene-controlled in vitro antibody responses to soluble antigens. T-cell colonies and monoclonal T-cell lines were generated which proliferated specifically in response to poly(LTyr,Glu)-poly(DLAla)--poly(LLys) [(T,G)-A--L] and were I-A restricted in these proliferative responses. These (T,G)-A--L-specific T-cell populations were evaluated for their ability to help unprimed and T-cell depleted spleen cell populations in the generation of antibody responses to trinitrophenyl (TNP)-(T,G)-A--L in vitro. It was found that long-term T-cell lines, including monoclonal T-cell populations derived by limiting dilution, were highly efficient helper cells for IgM responses to TNP-(T,G)-A--L. These helper T cells were both antigen-specific and I-A restricted in their ability to be activated and to cooperate with T-cell depleted spleen cell populations. Once specifically activated, however, these clones provided help that was antigen nonspecific. These studies have thus demonstrated the ability of antigen-specific and H-2-restricted monoclonal T-cell populations to provide help for responses to soluble antigens in vitro.

Induction of idiotype-bearing, nuclease-specific helper T cells by in vivo treatment with anti-idiotype

Treatment of BALB/c mice with purified pig anti-(BALB/c anti-nuclease) anti-idiotypic antibodies has been found to induce the appearance of idiotype-bearing immunoglobulins (Id') in the serum of these mice in the absence of detectable antigen binding activity. This phenomenon appeared to require T cells in the hosts because no Id' was detected in the serum of nude mice similarly treated. Furthermore, the spleens of BALB/c mice treated with anti-idiotype were found to contain helper T cells capable of providing help in an in vitro plaque-forming cell response to trinitrophenyl-nuclease equivalent to that provided by helper T cells from the spleens of nuclease-primed animals. Helper T cells from both anti-idiotype-treated and nuclease-treated animals were found to be antigen-specific and to be similarly susceptible to elimination by treatment with anti-idiotype plus complement. Therefore, treatment with both antigen and anti-idiotype appeared to prime similar populations of antigen-specific helper T cells, while having different effects on the induction of antibody. These findings are consistent with the network theory of receptor interactions in the immune response, and may provide a means for studying individual cell populations involved in such interactions.

Self recognition in allogeneic radiation bone marrow chimeras. A radiation-resistant host element dictates the self specificity and immune response gene phenotype of T-helper cells

The specificity of the self-recognition repertoire in fully allogeneic (A {arrow} B), semiallogeneic (A {arrow} A x B and A x B {arrow} A), and double donor (A + B {arrow} A) radiation bone marrow chimeras was assessed by the ability of their spleen cells to generate in vitro primary plaque-forming cell (PFC) responses to trinitrophenyl- keyhole limpet hemocyanin. In contrast to spleen cells from semiallogeneic and double donor chimeras, intact spleen cells from fully allogeneic BI0 {arrow} B10.A and B10.A {arrow} B10 chimeras were not capable of generating responses to trinitrophenyl (TNP)-keyhole limpet hemocyanin. However, cultures containing a mixture of both B10 {arrow} B10.A and B10.A {arrow} B10 spleen cells did respond, demonstrating that all the cell populations required for the in vitro generation of T-dependent PFC responses were able to differentiate into functional competence in a fully allogeneic major histocompatibility complex (MHC) environment. The self recognition repertoire of T-helper cells from fully allogeneic A {arrow} B chimeras was determined to be specific for the recognition of host, not donor, MHC determinants in that they were able to collaborate with cells expressing only host MHC determinants but not with cells expressing only donor MHC determinants, even though the functional lymphocytes in these chimeras were shown to be of donor origin. Experiments utilizing double donor A + B {arrow} A chimeras further demonstrated that the ability of chimeric T cells to recognize allogeneic MHC determinants as self structures was a function of a radiation-resistant host element and not simply a consequence of the tolerization of T cell precursors to allogeneic MHC determinants, because strain A lymphocytes isolated from A + B {arrow} A chimeras were tolerant to both A and B MHC determinants but were restricted to the self recognition of syngeneic host type A MHC determinants. Finally, the Ir gene phenotype expressed by B10 {arrow} B10.A and B10.A {arrow} B10 chimeric lymphocytes was determined by their ability to function in the Ir gene controlled response to TNP-poly-L-(Tyr,Glu)-poly-D,L-Ala-poly- L-Lys [(T,G)-A--L]. The ability of lymphocytes to function in TNP-(T,G)-A--L responses was not determined by their genotype but rather paralleled the specificity of their self recognition repertoire for high responder (H-2 (b)) determinants. The possible degeneracy of the MHC-specific self recognition repertoire is discussed, and a model is proposed for Ir gene regulation in which expression of Ir gene function by lymphocytes is an antigen-nonspecific consequence of the specificity and cross-reactivity of their self recognition repertoire.

Fine specificity of genetic regulation of guinea pig T lymphocyte responses to angiotensin II and related peptides

Guinea pig T lymphocyte responses to the octapeptide antigen angiotensin II (NH(2)-Asp(1)-Arg(2)-Val(3)-Tyr(4)-Ile(5)-His(6)-Pro(7)-Phe(8)-OH; AII) were examined using various synthetic peptide analogues and homologues. Each peptide antigen was assessed for immunogenicity and antigenicity in strain 2 and strain 13 guinea pigs as determined by in vitro T cell proliferative responses. The genetic control of T cell responses to these peptides was found to be highly specific and capable of distinguishing subtle differences in the antigens. For example, strain 2 guinea pigs responded to AII and were low responders to [Val(5)]-AII, whereas strain 13 animals responded to [Val(5)]-AII but not to AII. The genetic control in this case involved the difference of one methyl group between Val(5) and Ile(5). Differences in T cell responsiveness by strain 2 and strain 13 guinea pigs were also observed with analogues involving para substitutions on the phenyl ring of Tyr(4) and of Phe(8). However, the genetic regulation of T cell responses did not seem to be based on a single peptide residue. For example, removal of Asp(1) allowed strain 13 animals to respond to the Ile(5)-containing analogue, but eliminated responsiveness to the Val(5)-containing analogue. Thus, the first and fifth AII residues are both involved in the regulation of strain 13 T cell responses. Substitutions for Tyr(4) and Phe(8) suggested that the same residue may serve to alter the specificity of T cell responses in one strain, and determine responsiveness or unresponsiveness in the other strain. One of the most striking observations is that T cell responsiveness to the various AII analogues and homologues randomly fluctuates between strain 2 and strain 13 guinea pigs, and in general neither strain responds to the same peptide antigens. This suggests that strain 2 and strain 13 T cell responses are rarely directed against the same antigenic determinants, and that the T cell antigen-combining diversity is usually exclusive between these two strains. These results are discussed with respect to the specificity of Ir gene control and the relationship between Ir gene function and antigen recognition by T cells. Note added in proof: More recent experiments using a new lot of [Val(5)]- AII have indicated that [Val(5)]-AII-immune strain 2 T cells show significant stimulation with AII but remain relatively low responders with [Val(5)]-AII, as shown in Table I. The difference in priming for cross-reactivity for AII with the different lots of [Val(5)]-AII is at present unknown.

Role of accessory cells in B cell activation. III. Cellular analysis of primary immune response deficits in CBA/N mice: presence of an accessory cell-B cell interaction defect

The effect of the X-linked CBA/N genetic defect on the ability of mice to generate primary responses to thymic-dependent and thymic-independent antigens was assessed by comparing the ability of abnormal (CBA/N x DBA/2)F1 male mice and normal (DBA/2 x CBA/N)F1 male mice to generate 2,4,6-trinitrophenyl (TNP)-specific plaque-forming cell responses to TNP-keyhole limpet hemocyanin (KLH), TNP-conjugated Ficoll (TNP-Ficoll), TNP-Brucella abortus (BA), and TNP-lipopolysaccharide (LPS). The reciprocal F1 combinations used in this study differ genetically only in the origin of their X chromosome, but differ immunologically in that (CBA/N x DBA/2)F1 male mice express all the CBA/N immune abnormalities, whereas (DBA/2 x CBA/N)F1 male mice are immunologically normal. Analysis of thymic-dependent responses to TNP-KLH revealed that abnormal F1 mice were capable of generating primary responses in vivo to high doses of TNP-KLH, but failed to generate responses to suboptimal doses of TNP-KLH that were still immunogenic for normal F1 mice. Furthermore, under limiting in vitro micro-culture conditions, the abnormal F1 mice failed to generate primary thymic-dependent responses to any dose of TNP-KLH, even though under the identical conditions normal F1 mice consistently responded to a wide antigen dose range. The cellular basis of the failure of abnormal F1 mice to respond in vitro to TNP-KLH was investigated by assaying the ability of purified populations of accessory cells, T cells, and B cells from these mice to function in responses to TNP-KLH. The results of these experiments demonstrated that helper T cells and antigen-presenting accessory cells from abnormal F1 mice were competent and functioned as well as the equivalent cell populations from normal F1 mice. Instead, the failure of CBA/N mice to generate primary in vitro responses to TNP-KLH was solely the result of a defect in their B cell population such that B cells from these mice failed to be triggered by competent helper T cells and/or competent accessory cells. Similarly, the failure of abnormal F1 mice to respond either in vivo or in vitro to TNP-Ficoll was not the result of defective accessory cell presentation of TNP-Ficoll, but was the result of the failure of B cells from these mice to be activated by competent TNP-Ficoll-presenting accessory cells. In contrast to the failure of B cells from abnormal F1 mice to be activated in vitro in response to either TNP-KLH or TNP-Ficoll, B cells from abnormal F1 mice were triggered to respond to TNP-BA and TNP-LPS, antigens that did not require accessory cell presentation. The specific failure of B cells fron abnormal F1 mice to be activated in responses that required antigen-presentation by accessory cells suggested the possibility that the X-linked CBA/N genetic defect resulted in B cell populations that might be deficient in their ability to interact with antigen-presenting accessory cells...

Nature of T lymphocyte recognition of macrophage-associated antigens. V. Contribution of individual peptide residues of human fibrinopeptide B to T lymphocyte responses

Guinea pig T lymphocyte responses to a decapeptide antigen (NH1-Asp5-Ans6-Glu7-Glu8-Gly9-Phe10-Phe11-Ser12-Ala13-Arg14-OH) of human fibrinopeptide B (hFPB) were examined using various synthetic peptide analogues containing single residue substitutions. Each analogue was examined for antigenicity as determined by an in vitro proliferative responses of hFPN-immune strain 2 guinae pig T cells. In addition, both strain 2 and strain 13 animals were immunized with each analogue and immunogenicity assessed by in vitro T cell-proliferative responses with the homologous immunizing analogue and the parent peptide. Replacement of arginine14 with lysine formed an immunogenic analogue which showed no antigenic cross-reactivity with the native peptide in strain 2 T cell responses. In addition, substitution of arginine14 with blocked lysine again produced a unique immunogenic analogue that showed little or no antigenic identity with the intact lysine analogue or the native peptide. In similar fashion, substitution of resideu phenylalanie10 with tyrosine or Phe(4-NO2) created unique immunogenic analogues with little or no antigenic identity to the native peptide with strain 2 T cells. By contrast, replacement of phenylalanine11 with either tyrosine or Phe(4-NO2) resulted in analogues with a total loss of immunogenicity and antigenicity in strain 2 T cell responses. An analogue in which glutamic acid7,8 were replaced with glutamine retained a small degree of antigenicity with hFPB-immune T cells, but T cells from strain 2 animals immunized with the Gln analogue responded only marginally to the Gln analogue while producing good proliferative responses with the native peptide. On the other hand, an analogue in which asparatic acid5 was replaced with asparagine retained most of the antigenic identity with hFPB for strain 2 T cell responses. None of thee analogues were immunogenic for strain 13 guinea pigs. These observations are discussed with respect to the contribution of each substituted residue to T cell respones, mechanism of Ir gene function, and a model for T cell recognition of small peptide antigens.

Genetic regulation of delayed-type hypersensitivity responses to poly(LTyr,LGu)-poly(DLAla)--poly(LLys). I. Expression of the genetic defect at two phases of the immune process

Delayed-type hypersensitivity (DTH) responses served in this study as an experimental model for the analysis of genetic regulations of T-cell responses. Educated irradiated cells from H-2b mice mediated responses in syngeneic recipients, whereas mice of the a, d, f, k, and s haplotypes were nonresponders to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L]. These results suggest that cell-mediated immune responsiveness to (T,G)-A--L is linked to the H-2 complex, as was shown for humoral responses. Educated irradiated T cells of F1 hybrids between high and low responders mediated DTH responses, which indicates that the gene(s) controlling the DTH responses is dominant. To analyze the genetic defect in DTH responses to (T,G)-A--L, we separated the T-cell activation phase from the effector phase that was determined in recipient mice. Two types of nonresponders were observed: (a) When lymphocytes of the a or k haplotypes were educated in a syngeneic environment and then transferred into hybrids between the parental (nonresponder x responder) F1 recipients, DTH responses could have been manifested. (b) On the other hand, no DTH responses could be mediated by transferring educated cells of the H-2s or H-2f origin into the appropriate F1 recipients. In addition, irradiated F1 cells that had been activated to (T,G)-A--L could not mediate DTH responses in both types of nonresponder recipients. These results suggest that T cells of H-2k or H-2a mice can be activated to generate DTH responses to (T,G)-A--L and that the defect in these mouse strains is expressed in another cell population needed for the manifestation of the DTH reaction in the recipient mice. In contrast, T cells of H-2s and H-2f origin cannot be activated to (T,G)-A--L and, thus, fail to manifest DTH responses.

An immunologic network

The immune system is a complex network of molecules and cells specifically connected by the complementarity of receptors for antigen and receptors for receptors. The network includes multiple positive- and negative-feedback loops, which modulate the type, magnitude, and duration of responses. The great challenge is to devise ways to manipulate the system specifically to induce effective autoimmunity to cancer, to prevent allograft rejection, and to turn off undesirable responses in allergies and autoimmune diseases. Recognition of the immune system as a network helps to explain why these objectives are so difficult and why manipulation of multiple components to achieve desired regulation may be required. But presumably manipulation must be focused on connectivity between receptor for epitope and receptor for receptor to achieve a high degree of specific regulation.

Impairment of antigen-presenting cell function by ultraviolet radiation

UV light irradiation of BALB/c mice was found to result in impairment of antigen-presenting cell function. Adherent trinitrophenyl-derivatized cells from the peritoneal exudate cell population or the spleen of UV-treated donors could not induce hapten-specific delayed hypersensitivity responses in UV-irradiated syngeneic mice, whereas adherent trinitrophenyl-derivatized cells from normal mice were able to do so. The failure to induce immunity in UV-treated mice by utilizing UV-treated adherent antigen-presenting cells was associated with the development of antigen-specific suppressor T cells. The implication of these results for UV-induced carcinogenesis is discussed.

H-2-linked genetic control of murine T-cell-mediated lympholysis to autologous cells modified with low concentrations of trinitrobenzene sulfonate

Spleen cells from B10.BR and C57BL/10 (B10) mice were compared for their ability to generate primary in vitro cytotoxic responses to syngeneic cells modified with different concentrations (from 10 to 0.031 mM) of trinitrobenzene sulfonate (TNBS) (TNP-self). Although both strains generated effector cells to TNP-self in the range of 10-0.25 mM TNBS modification, effector activity of B10 cells was weaker than that of B10.BR cells. B10 spleen cells did not respond to syngeneic stimulating cells modified at 0.1 mM or lower, whereas B10.BR cells generated effector activity even when stimulated by TNP-self modified with as low as 0.031 mM TNBS. Fluorescence analysis of the modified cells using the FACS II indicated that equivalent quantities of TNP were conjugated to the surfaces of B10.BR and B10 spleen cells for any given concentration of TNBS modification. Similar strain-dependent differences were observed when the TNP was diluted out in the cultures by reducing the number of stimulating cells modified with 10 mM TNBS. These response patterns were verified by stimulating cultures of B10.BR and B10 spleen cells either with TNP conjugated to bovine serum albumin or bovine gamma globulin (B10.BR but not B10 cells responded to TNP-conjugated proteins) or with TNBS-modified glass-adherent spleen cells. The strain-dependent differences could also be detected at the effector phase, because optimally stimulated B10.BR, but not B10 effector cells, could lyse 0.1 mM TNBS-modified syngeneic target cells. The genetic parameters associated with the response and nonresponse patterns of B10.BR and B10 mice were further investigated by comparing the cytotoxic responses to low doses of TNP-self of spleen cells from the following strains: (a) C3H/HeJ (H-2k) and C3H.SW (H-2b); (b) BALB.K (H-2k) and BALb.b (h-2b); and (c) B10.A (H-2a) and B10.D2 (H-2d). The H-2k and H-2a, but not the H-2b and H-2d, strains generated cytotoxic responses to TNP-self when the syngeneic stimulators were modified with 0.1 mM TNBS. Further studies using (B10 X B10.BR)F1 responding cells and parental or F1-modified stimulating cells, indicated that the F1 cells generated cytotoxic activity to low doses of TNP in association with H-2k but not in association with H-2b self products. The results of this study indicate that H-2-linked genetic factors, expressed in the target as well as in the responding and/or stimulating cell populations, control the ability of inbred mouse strains to generate cytotoxic effector cells to low doses of TNP-self. Such dose-dependent genetic effects may be important in the regulation of immune responses activated in vivo by chronic exposure to infectious agents.

Cellular and genetic control of antibody responses. V. Helper T-cell recognition of H-2 determinants on accessory cells but not B cells

Requirements for helper T-cell recognition of H-2 determinants expressed on adherent accessory cells and on B cells was individually assessed in the anti-hapten PFC responses to TNP-KLH. Complicating allogeneic effects were minimized or avoided by the use of helper T cells from normal F1 hybrids, parent leads to F1 chimeras, and F1 leads to parent chimeras. The results of both in vitro and in vivo experiments demonstrated that: (a) helper T cells are not required to recognize the identical H-2 determinants on both accessory cells and B cells; (b) helper T cells are required to recognize K or I-A region-encoded determinants expressed on accessory cells; (c) no requirement was observed in vitro or in vivo for helper T-cell recognition of B-cell-expressed H-2 determinants; and (d) no requirement was observed for H-2 homology between accessory cells and B cells. The absence of required helper T-cell recognition of the identical H-2 determinants on both accessory cells and B cells was demonstrated in two ways: (a) naive of KLH-primed (A x B)F1 hybrid helper T cells collaborated equally well with B cells from either parentA or parentB in the presence of accessory cells from either parent; (b) A leads to (A x B)F1 chimeric spleen cells depleted of accessory cells collaborated equally well with accessory cells from either parentA or parentB, even though the B cells only expressed the H-2 determinants of parentA. A requirement for helper T-cell recognition of K or I-A region-encoded H-2 determinants on accessory cells was also demonstrated in two ways: (a) (A x B)F1 leads to parentA chimeric spleen cells depleted of accessory cells collaborated with accessory cells from parentA but not parentB; and (b) (A x B)F1 leads to parentA chimeric helper T cells collaborated with normal F1 B cells only in the presence of parental or recombinant accessory cells that expressed the K or I-A region-encoded determinants of parentA. Although restricted in their ability to recognize H-2 determinants on accessory cells, it was demonstrated both in vitro and in vivo that (A x B)F1 leads to parentA chimeric helper T cells were able to collaborate with B cells from either parentA or parentB. In vitro in the presence of accessory cells from parentA, (A x B)F1 leads to parentA chimeric helper T cells collaborated equally well with B cells from either parent. In addition, the inability of (A x B)F1 leads to parentA chimeric helper T cells to collaborate with (B + accessory) cells from parentB was successfully reversed by the addition of parentA SAC as added accessory cells. In vivo, upon the addition of parentA accessory cells, (A x B)F1 leads to parentA chimeric helper T cells collaborated with parentB B cells in short-term adoptive transfer experiments.

Close association between particular I region-determined cell surface antigens and Ir gene-controlled immune responsiveness to synthetic polypeptides in wild rats

The relationship between major histocompatibility complex (MHC) and genetic control of immune responsiveness to the synthetic polypeptides (T,G)-A--L [poly-(LTyr,LGlu)-poly(DLAla)--poly(LLys)] and (H,G)-A--L [poly(LHis,L-Glu)-poly-(DLAla)--poly(LLys)] has been studied in 26 wild rats. The major histocompatibility complex (MHC) genotype frequencies observed were not different from those expected according to the Hardy-Weinberg formula. More than half of the wild rats carried MHC-linked responder Ir-TGAL and Ir-HGAL genes. High or intermediate responsiveness to (T,G)-A--L and high responsiveness to (H,G)-A--L were always found to be associated with particular I region-determined cell surface antigens. These antigens could be identified serologically and by primary and secondary mixed lymphocyte reactions, and were similar or identical to I region products of (T,G)-A--L high responder or (H,G)-A--L intermediate responder inbred rat strains. The strong association between cell surface antigens and immune responsiveness could be due to linkage disequilibrium or to pleiotropy. Since the same I region-determined cell surface structure could be associated either with high or intermediate anti-(T,G)-A--L antibody titers, the presence of the Ia antigen(s) identified did not seem to guarantee high antibody responsiveness to the test antigen.

The role of H-2-linked genes in helper T-cell function. VI. Expression of Ir genes by helper T cells

We examined the expression of (TG)-A--L specific Ir genes in helper T cells using T cells from low responder leads to (B10, high responder x low responder) F1 chimeric mice. In this paper, the low responder strain studied was B10.M, H-2f. B10.M T cells from these chimeric animals do not help anti-TNP-(TG)-A--L responses, even though they have matured in a high responder thymus and been primed and challenged with antigen on high responder Mphi and B cells. These findings indicate that in the H-2f haplotype an Ir-gene controlling anti-(TG)-A--L activity is expressed in helper T cells. The findings are in contrast to those we have obtained and previously reported with T cells of another low responder haplotype, H-2a. Taken together with our previous findings that (TG)-A--L specific Ir genes are expressed by B cells and Mphi of both the H-2a and H-2f haplotypes, the results indicate two sites of action for Ir genes, and suggest two different gene products acting at different stages of the response, both of which are defective in H-2f cells, and only one of which is defective in H-2a cells.

The role of H-2 linked genes in helper T-cell function. IV. Importance of T-cell genotype and host environment in I-region and Ir gene expression

We have studied the properties of helper T cells specific for sheep erythrocytes (SRBC), keyhole limpet hemocyanin (KLH), or poly-L-(Tyr,Glu)-poly-DL-Ala-poly-L-Lys [(T,G)-A--L]. These T cells differentiated and were primed in vivo in irradiation chimeras constructed of various combinations of F1 and parental bone marrow donors and irradiated recipients. Primed T cells were then tested for helper activity in the in vitro response of B cells and macrophages (Mphi) of parental or F1 origin to the hapten trinitrophenol coupled to the priming antigen. When testing either SRBC or KLH-specific T cells of parental H-2 type which had differentiated in F1 hosts, we found that they cooperated equally well with B cells and Mphi of either parental H-2 type. On the other hand, when testing F1 T cells which had differentiated in parental hosts, we found that they cooperated well only with B cells and Mphi which had the K-IA region type of the parental host. In similar experiments we found that (T,G)-A--L-specific T cells of low responder H-2 type which had differentiated in (high responder X low responder) F1 hosts induced high responses in high responder B cells and Mphi (T,G)-A--L-specific F1 T cells which differentiated in high responder but not those which differentiated in low responder hosts induced high responses in high responder B cells and Mphi. Low responder B cells and Mphi yielded low responses in all cases regardless of the source of (T,G)-A--L-specific T cells with what they were tested. Our results support the conclusion that I-region and Ir genes function via their expression in B cells and Mphi and in the host environment during helper T-cell differentiation, but not, at least under the conditions of these experiments, via their expression in the helper T cell itself. These findings place constraints upon models which attempt to explain the apparent dual recognition of antigen and I-region gene products by helper T cells.

Suppressor T-cell activity in responder X nonresponder (C57BL/10 X DBA/1)F1 spleen cells responsive to L-glutamic acid60-L-alanine30-L-tyrosine10

The ability of spleen cells from (responder X nonresponder)F(1) mice immunized with various GAT-Mphi, GAT-MBSA, and soluble GAT to develop IgG GAT-specific PFC responses in vitro after stimulation with responder and nonresponder parental and F(1) GAT-Mphi, was investigated. F(1) spleen cells from mice immunized with F(1) GAT-Mphi or GAT-MBSA developed secondary responses to responder and nonresponder parental and F(1) GAT- Mphi, but not to unrelated third party GAT-Mphi. Spleen cells from F(1) mice immunized with either parental GAT-Mphi developed secondary responses to F(1) GAT-Mphi and only the parental GAT-Mphi used for immunization in vivo. Soluble GAT-primed F(1) spleen cells responded to F(1) and responder parental, but not nonresponder parental, GAT-Mphi. Simultaneous immunization in vivo with the various GAT-Mphi or GAT-MBSA plus soluble GAT modulated the response pattern of these F(1) spleen cells such that they developed secondary responses only to F(1) and parental responder GAT-Mphi regardless of the response pattern observed after immunization with the various GAT-Mphi or GAT-MBSA alone. These observations demonstrate the critical importance of the physical state of the GAT used for immunization in determining the subsequent response pattern of immune F(1) spleen cells to the parental and F(1) GAT-Mphi. Further, suppressor T cells, capable of inhibiting primary responses to GAT by virgin F(1) spleen cells stimulated by nonresponder parental GAT-Mphi, were demonstrated in spleens of F(1) mice immunized with soluble GAT, but not those primed with F(1) GAT-Mphi. Because responder parental mice develop both helper and suppressor T cells after immunization with GAT-Mphi, and soluble GAT preferentially stimulates suppressor T cells whereas GAT-Mphi stimulate helper T cells in nonresponder parental mice, these observations suggest that distinct subsets of T cells exist in F(1) mice which behave phenotypically as responder and nonresponder parental T cells after immunization with soluble GAT and GAT- Mphi.