IgA allotype suppression in mice: A cellular implication for the IgA preponderance in the gut

Paternal IgA allotype suppressions were induced in (A/HeJ x SJL/J)F₁, (BALB/cJ x CB-20) F₁, and (BALB/cJ x SJL/J)F₁ mice by perinatal exposure of the neonates to antibody against paternal IgA allotype (Ig-2b). All the Ig-2b allotype suppressions were temporary and were prominently seen at the age of 4–10 weeks. These transient Ig-2b allotype suppressions were manifested by a suppression of Ig-2b allotype in the serum and a suppression of Ig-2b allotype-producing cells in the gut lamina propria. During the suppression, no replacement of the Ig-2b allotype by IgM and IgG plasma cells was seen in the gut lamina propria. The transient IgA allotype suppression was primarily due to a depletion of IgA allotype precursors in Peyer's patches; suppressor T cells were not actively involved. These results suggest that IgA preponderance in the gut is due to the migration of the patch IgA precursors and their accumulation and maturation in the gut lamina propria.     

Unidirectional IgG allotype- and isotype-specific suppressor cells in congeneic mice

By the use of allotypic markers on immunoglobulin molecules of isotypes IgG1 and IgG2a, in transfers of spleen cells between Igh haplotype congeneic partner strains BALB/c (Igha) and CB20 (=BALB/c-Ighb), the expression of donor and recipient lymphocytes could be followed differentially. BALB/c donor's allotype a was produced in nonirradiated CB20 recipients for months. By contrast, CB20 donor's allotype b disappeared in nonirradiated BALB/c recipients shortly after transfer. These BALB/c recipients of CB20 spleen cells ("CB20-primed") developed lymphocytes which were able to suppress the autochthoneous allotype b production of CB20 irradiated or CB20 nu/nu or neonatal F1 (BALB/c female X CB20 male) recipients immediately after transfer. Titers decreased with a half life of about 4 days, resembling that of immunoglobulin molecules. The suppression was restricted to the IgG2a isotype of allotype b. Neither the other isotype IgG1 of allotype b, nor, in the reciprocal transfer experiment, IgG1 or IgG2a of allotype a was affected. Analogous transfers between Igh congeneic partners on a C57B1/6 genomic background revealed the same susceptibility of allotype b-producing cells from C57B1/6 donors toward suppression by C57B1/6-Igha mice as recipients. Allotype suppression, induced by cell transfer, is thus unidirectional in that Igha haplotype mice react against allotype b but not vice versa, and it is isotype-specific, only directed against IgG2a, and not IgG1.     

Regulation of the production of murine IgG2a by an H-2-linked gene and other unlinked genes

Alleles of at least two loci (rig-1 and Rig-2) regulate the levels of serum immunoglobulin of the Igh-1b class and allotype in BALB/c Ig^b (BAB/14) and (BALB/c × BAB/14)F₁ mice. The combined effect of the BALB/c alleles at these two loci is to lower Igh-1b levels significantly below those observed in other strains and below their own levels of Igh-1a in allotype heterozygous mice. The rig-1 locus is closely linked to or within the H-2 complex. Two alleles have been defined: rig-1 ^d and rig-1 ^b in H-2 ^d and H-2 ^b haplotypes, respectively. Homozygous rig-1 ^d d animals heterozygous for the BALB/c Rig-2 allele(s) have very low levels of Igh-1b. The designation of Rig-2 is provisional since it has not been mapped or defined as a single locus.     

Role of CD40 in a T cell-mediated negative regulation of Ig production

To investigate the possible role of CD40 in a negative regulation of Ig production, we used the mouse Ig allotype suppression model. T splenocytes from IGH(a/a) mice are able in vivo to totally and chronically inhibit the production of IgG(2a)(b) (IgG2a from the IGH(b) haplotype). Accordingly, postnatal transfer of IGH(a/a) T splenocytes into histocompatible IGH(a/b) F(1) or congenic IGH(b/b) mice leads to a characteristic IgG(2a)(b) suppression. The helper action of anti-IgG(2a)(b) CD4(+) T cells is required for the recruitment of anti-IgG(2a)(b) CD8(+) T suppression effectors. The latter use perforin (pore-forming protein, Pfp)- and/or Fas-dependent cytotoxic pathways to continuously eliminate B cells recently committed to IgG(2a)(b) production. In the present study we first showed that in vivo agonistic anti-CD40 mAb treatment of IGH(a/a) mice, deprived of their CD4(+) T cell compartment, could bypass the help of Ig allotype-specific CD4(+) T cells and generate CD8(+) T effector cells able to strongly inhibit IgG(2a)(b) production. This result demonstrates the usefulness of CD40 triggering in setting up an immune regulatory mechanism. Furthermore, with regard to the suppression-effector mechanism, we demonstrated that B cell CD40 expression was required for full suppression establishment via the Fas-dependent pathway. Indeed, IGH(a/a) PFP(degrees/degrees) T cells (using exclusively the Fas pathway) induced full IgG(2a)(b) suppression against IGH(b/b) CD40(+/+) B cells, but only partial inhibition of IgG(2a)(b) production against IGH(b/b) CD40(degrees/degrees) B cells. This finding provides the first demonstration of direct involvement of B cell CD40 expression in in vivo negative control of an Ig production.     

In vitro immunoglobulin allotype synthesis by spleen cells of heterozygous rabbits. Specific suppression by anti-allotype antibody

The production of immunoglobulin (Ig) bearing the b4 and b5 allotypic markers by b⁴b⁵ heterozygous spleen cells cultured in vitro was assessed by means of a sensitive and reproducible radioimmunoassay. Ig synthesis was demonstrated by the increasing amounts of the b4 and b5 allotypes appearing with time in the supernatant fluids. To determine the effect of anti-b4 or anti-b5 antibody on the synthesis of the b4 and b5 allotypes, spleen cells from b⁴b⁵ heterozygous rabbits were incubated for 24 hr in the presence of anti-b4 or anti-b5 and then washed and cultured for an additional 4 days. Anti-b4 suppressed the production of the b4 allotype with no effect on b5 production, whereas anti-b5 suppressed the production of b5 allotype with no effect on b4 production. This suppression of allotype synthesis in vitro presumably results from an antigen-antibody reaction occurring on the surface of lymphoid cells by a mechanism which may be similar to that which brings about allotype suppression in vivo for fetal and newborn rabbits.     

Protective Effects of Mangosteen Extract on H2O2-Induced Cytotoxicity in SK-N-SH Cells and Scopolamine-Induced Memory Impairment in Mice

Mangosteen extracts (ME) contain high levels of polyphenolic compounds and antioxidant activity. Protective effects of ME against β-amyloid peptide (Aβ), induced cytotoxicity have been reported. Here, we further studied the protective effects of ME against oxidative stress induced by hydrogen peroxide (H₂O₂) and polychlorinated biphenyls (PCBs), and demonstrated the protection against memory impairment in mice. The cytoprotective effects of ME were measured as cell viability and the reduction in ROS activity. In SK-N-SH cell cultures, 200 μg/ml ME could partially antagonize the effects of 150 or 300 µM H₂O₂ on cell viability, ROS level and caspase-3 activity. At 200, 400 or 800 µg/ml, ME reduced AChE activity of SK-N-SH cells to about 60% of the control. In vivo study, Morris water maze and passive avoidance tests were used to assess the memory of the animals. ME, especially at 100 mg/kg body weight, could improve the animal’s memory and also antagonize the effect of scopolamine on memory. The increase in ROS level and caspase-3 activity in the brain of scopolamine-treated mice were antagonized by the ME treatment. The study demonstrated cytoprotective effects of ME against H₂O₂ and PCB-52 toxicity and having AChE inhibitory effect in cell culture. ME treatment in mice could attenuate scopolamine-induced memory deficit and oxidative stress in brain.     

Generation in vivo of non-T suppressor cells with the use of anti-allotype antibody

Anti-Igh-1b antiserum induced allotype-specific suppression of adult mouse spleen cells in an adoptive transfer system. Suppression of Igh-1b anti-sheep red blood cell plaque-forming cells was measured as late as 4 wk after the injection of allotype heterozygous (Igha/b) spleen cells, antiserum, and sheep red blood cells. Suppression was maintained on retransfer of the allotype-suppressed spleen cells to further irradiated recipients in the absence of additional exogenous anti-allotype antibody. Mixing experiments were performed to test the putative inhibitory effects of allotype-suppressed spleen cells from the first adoptive transfer (stage I) on the antibody response of normal spleen cells in a second adoptive transfer (stage II). No suppression was observed by using unfractionated stage I spleen cells. In contrast, when these allotype-suppressed spleen cells were depleted of T cells, they strongly inhibited the antibody production of admixed normal spleen cells in stage II. This inhibitory activity of antibody-induced stage I spleen cells was directed primarily toward the target allotype, but some suppression of the Igh-1a plaque-forming cell response and total IgG production also occurred. Although removal of adherent cells did not affect the inhibitory activity of allotype-suppressed spleen cells from stage I, removal of Ig+ cells completely abrogated the inhibitory activity. These results suggest that antibody-induced regulatory B cells may play a role in maintaining long term allotype suppression.     

Mycobacterium tuberculosis-specific CD4+, IFNgamma+, and TNFalpha+ multifunctional memory T cells coexpress GM-CSF

Multifunctional T cells expressing several cytokines in parallel are thought to play a crucial role in protection against different infections. To characterize T cell cytokine patterns associated with disease and protection in Mycobacterium tuberculosis infection we determined the expression of IFNγ, IL-2, TNFα, and GM-CSF in T cell subpopulations from children with tuberculosis (TB) and healthy latently M. tuberculosis-infected children (LTBI) after short-term in vitro restimulation. We identified CD4⁺ effector memory T cells (T_EM) as the major source of all measured cytokines after antigen-specific restimulation. T_EM from children with TB expressed higher proportions of IFNγ, TNFα, and IL-2 after Mtb restimulation while no differences were detected for GM-CSF between both study groups. GM-CSF secretion strongly depended on antigen-specific stimulation. Analyses of multiple cytokine patterns revealed that the majority of GM-CSF-positive M. tuberculosis-specific memory T cells coexpressed IFNγ and TNFα therefore showing a characteristic feature of multifunctional T cells. We conclude that children with active TB possess higher proportions of IFNγ-, TNFα-, and/or IL-2-positive T_EM than children with LTBI while GM-CSF coexpression reveals a novel subpopulation within CD4⁺ memory T cells not increased in children with active TB.     

Genetics and expression of kappa-type light chains in Basilea rabbits

In contrast to rabbits of b4, b5, b6, and b9 allotypes whose serum immunoglobulins (Igs) are predominantly composed of kappa-type light chains, rabbits of the mutant Basilea strain have serum Igs that are largely of lambda type. We prepared several antisera that recognized a minor K2 (bas) light chain that is produced by Basilea rabbits. With these antisera we identified the K2 (bas) isotype in the serum of the original b ⁹/b ⁹ male rabbit whose offspring displayed the Basilea mutant phenotype. It was present in one half of his nonmutant offspring which inherited b9 from him and another b allotype from their mothers. Breeding was conducted both in Basel and at the NIH to develop and maintain colonies of mutant Basilea strain rabbits. The data obtained during colony development confirm that the trait of expression of the bas allotype maps to the same genetic region (b locus) that is known to control the allelic b allotypes b4, b5, b6 and b9. Homozygotes or heterozygotes of b4, b5 or b6 allotype (b ^b /b ^b ) were mated with homozygous b ^bas /b ^bas rabbits to produce F₁s, and then F₂s as well as progeny of backcrosses to both homozygous parental types (b ^b /b ^b and b ^bas /b ^bas ) were produced. The bas allotype segregates as an allele (or pseudoallele) at the b locus although there was a deficiency in recovery of homozygous bas offspring in both the F₂ and backcross matings to b ^bas /b ^bas parental type in the NIH colony. This selective deficiency may reflect a deleterious effect on survival of homozygous bas progeny.The Basel Institute for Immunology was founded and is supported by F. Hoffmann La-Roche and Co., Ltd., Basel, Switzerland.     

Genetic control of murine hemagglutinin formation to H-2.5

When B10.D2 (H-2^d) mice are immunized with lymphoid cells from C57B1/10 (H-2 ^d ) and their antisera tested against B10.A (H-2 ^a ) target cells, only antibodies to H-2.5 are measured. The same is true for immunization of DBA/2 (H-2 ^d ) mice when their antisera are absorbed with B10.D2 cells prior to testing. Irrespective of the dose of immunogen administered, the primary hemagglutinin response of B10.D2 mice is significantly lower than that of DBA/2 mice and (B10.D2 × DBA/2)F₁ hybrids, but the secondary responses are similar. The low responsiveness of B10.D2 mice appears to be determined by a single dominant gene with incomplete penetrance; the gene is not linked to eitherH- 2, Hc, or the immunoglobulin allotype loci. In addition, the H-2.5 hemagglutinin response is susceptible to nongenetic influences. When antisera from B10.D2, devoid of H-2.5 hemagglutinins, were assayed in a complement-mediated cytotoxic test, they contained almost as much anti-H-2.5 activity as did the antisera from DBA/2 mice or (B10.D2 × DBA/2)F₁ hybrids. The possibility is discussed that the locus responsible for the deficient primary hemagglutinin response of B 10.D2 may not be determinant-specific but may affect hemagglutinin responses in general.     

Expression of the Mucosal Homing Receptor α4β7 Correlates with the Ability of CD8+ Memory T Cells To Clear Rotavirus Infection

The integrin α₄β₇ plays an important role in lymphocyte homing to mucosal lymphoid tissues and has been shown to define a subpopulation of memory T cells capable of homing to intestinal sites. Here we have used a well-characterized intestinal virus, murine rotavirus, to investigate whether memory/effector function for an intestinal pathogen is associated with α₄β₇ expression. α₄β₇^hi memory phenotype (CD44^hi), α₄β₇⁻ memory phenotype, and presumptively naive (CD44^lo) CD8⁺ T lymphocytes from rotavirus-infected mice were sorted and transferred into Rag-2 (T- and B-cell-deficient) recipients that were chronically infected with murine rotavirus. α₄β₇^hi memory phenotype CD8⁺ cells were highly efficient at clearing rotavirus infection, α₄β₇⁻ memory cells were inefficient or ineffective, depending on the cell numbers transferred, and CD44^lo cells were completely unable to clear chronic rotavirus infection. These data demonstrate that functional memory for rotavirus resides primarily in memory phenotype cells that display the mucosal homing receptor α₄β₇.     

The allotypic patchwork pattern of the rabbit IGKC1 allele b5wf: genic exchange or common ancestry?

 The protein sequences of different alleles of the rabbit immunoglobulin IGKC1 gene can differ at more than 40% of the amino acid positions. This exceptional degree of allelic divergence raises questions concerning the causal underlying mechanisms. We report the DNA sequence of the coding region of an allotype which is associated with the mitochondrial lineage A (Southwestern Spain). At the serological level, this b5wf allotype presents a patchwork of antigenic determinants which in domestic breeds are characteristic of the b4, b5, and b6 allotypes. The inferred protein sequence of the b5wf allotype was found to differ from that of the b4, b5, and b6 allotypes at 25, 10, and 15% of the amino acid positions, respectively. Sequence comparisons show that the b4-specific epitopes of the b5wf allotype are probably due to a shared ThrThrGlnThr motif at Kabat positions 153–156. Similarly, the shared b5-specific determinants should relate to the motifs 161ThrSerLys163 and/or 182LysSerAspGlu185. A monoclonal antibody binding epitope shared among the b5wf, b5, and b6 sequences appeared to be correlated with the presence of Asp190. Although there is evidence of interallelic genic exchange, sequence comparisons suggest that the apparent mosaic structure of the b5wf allotype is better explained by common ancestry and point mutation. Received: 22 June 1998 / Revised: 18 August 1998     

IFN-β Inhibits the Increased Expression of IL-9 during Experimental Autoimmune Uveoretinitis

Purpose

It has been shown that IL-9 plays a proinflammatory role in the pathogenesis of certain autoimmune diseases. This study was designed to investigate the possible role of IL-9 in the development of experimental autoimmune uveoretinitis (EAU) and the effect of IFN-β on its expression.

Methods

EAU was induced in B10RIII mice by immunization with interphotoreceptor retinoid-binding protein peptide 161–180 (IRBP_161–180). IFN-β was administered subcutaneously to IRBP_161–180 immunized mice every other day from day one before immunization to the end of the study. Splenocytes and draining lymph node (DLN) cells from EAU mice or control mice or EAU mice treated with IFN-β or PBS were stimulated with anti-CD3/CD28 or IRBP_161–180 for 3 days. Naïve T cells cultured under Th1 or Th17 polarizing conditions were incubated in the presence or absence of IFN-β for 4 days. Effector/memory T cells were activated by anti-CD3/CD28 in the presence or absence of IFN-β for 3 days. IFN-β-treated monocytes were cocultured with naïve T cells or effector/memory T cells for 3 days. Culture supernatants were collected and IL-9 was detected by ELISA.

Results

IL-9 expression in splenocytes and DLN cells was increased in EAU mice during the inflammatory phase and returned back to lower levels during the recovery phase. IFN-β in vivo treatment significantly inhibited EAU activity in association with a down-regulated expression of IL-9. In vitro polarized Th1 and Th17 cells both secreted IL-9 and the addition of IFN-β suppressed production of IL-9 by both Th subsets. Beside its effect on polarized Th cells, IFN-β also suppressed the secretion of IL-9 by effector/memory T cells. However, IFN-β-treated monocytes had no effect on the production of IL-9 when cocultured with naïve or effector/memory T cells.

Conclusion

IL-9 expression is increased during EAU which could be suppressed by IFN-β.     

Proliferation-Linked Apoptosis of Adoptively Transferred T Cells after IL-15 Administration in Macaques

The adoptive transfer of antigen-specific effector T cells is being used to treat human infections and malignancy. T cell persistence is a prerequisite for therapeutic efficacy, but reliably establishing a high-level and durable T cell response by transferring cultured CD8⁺ T cells remains challenging. Thus, strategies that promote a transferred high-level T cell response may improve the efficacy of T cell therapy. Lymphodepletion enhances persistence of transferred T cells in mice in part by reducing competition for IL-15, a common γ-chain cytokine that promotes T cell memory, but lymphodepleting regimens have toxicity. IL-15 can be safely administered and has minimal effects on CD4⁺ regulatory T cells at low doses, making it an attractive adjunct in adoptive T cell therapy. Here, we show in lymphoreplete macaca nemestrina, that proliferation of adoptively transferred central memory-derived CD8⁺ effector T (T_CM/E) cells is enhanced in vivo by administering IL-15. T_CM/E cells migrated to memory niches, persisted, and acquired both central memory and effector memory phenotypes regardless of the cytokine treatment. Unexpectedly, despite maintaining T cell proliferation, IL-15 did not augment the magnitude of the transferred T cell response in blood, bone marrow, or lymph nodes. T cells induced to proliferate by IL-15 displayed increased apoptosis demonstrating that enhanced cycling was balanced by cell death. These results suggest that homeostatic mechanisms that regulate T cell numbers may interfere with strategies to augment a high-level T cell response by adoptive transfer of CD8⁺ T_CM/E cells in lymphoreplete hosts.     

Induction of primary and inhibition of secondary antibody response to hapten by hapten conjugates of type III pneumococcal polysaccharide.

Tri- or dinitrophenylated pneumococcal polysaccharide type III (TNP- or DNP SIII)) induced a primary 19S anti-TNP response without generating immunological memory to the hapten in LAF₁ mice. Hapten-hemocyanin (TNP-KLH) or hapten conjugates of B. abortus organisms (DNP-BA) induced both 19S and 7S primary responses and memory to the hapten. Spleen cells from mice immunized with TNP-KLH or DNP-BA did not give adoptive memory responses upon challenge with hapten-SIII and, in fact, were inhibited from responding to their homologous hapten conjugates by simultaneous injection of hapten-SIII. Incubation of TNP-KLH-primed spleen cells for as short as 5 min at 0 °C with 10 μg of TNP-SIII per milliliter virtually abolished their ability to give 19S and 7S memory responses to TNP-KLH upon transfer into irradiated recipients. It is suggested that a difference in avidity and/or number of anti-TNP receptors per cell between virgin and primed B cells may be an important factor in determining whether the cells will be stimulated or inhibited by exposure to hapten-SIII. Another factor may be a difference between virgin and memory cells in their requirement for T-cell help.     

Adoptive transfer of CD3+ T cells and CD4+CD44high memory T cells induces autoimmune pancreatitis in MRL/MpJ mice

The immunopathogenesis of autoimmune pancreatitis (AIP) is poorly understood. Here, we have used MRL/MpJ mice, a model of spontaneous AIP, to address the role of cellular autoimmune processes in the initiation and progression of the disease. Therefore, different T cell subpopulations were adoptively transferred from sick to still healthy (but susceptible) MRL/MpJ mice. Unpurified splenocytes and CD3⁺ T cells both efficiently induced AIP, while CD4⁺ and CD8⁺ T cells alone, as well as splenocytes from healthy mice, were insufficient to trigger the disease. Strikingly, CD4⁺CD44^high memory T cells, although transferred at lower numbers than other T cells, also induced AIP in recipient mice. Employing a modified experimental design, we also evaluated the effects of regulatory T cells (T_regs) on the progression of AIP in already diseased mice. Under the given experimental conditions, there was no significant suppressive effect of adoptively transferred T_regs on pancreatic histopathology. The results of our studies suggest a key role of T cell‐mediated processes in murine AIP. The effects of CD4⁺CD44^high memory T cells are in accordance with genetic studies of our group, which had previously implicated this cell type into the pathogenesis of AIP. In follow‐up studies, we will focus on the interplay of cellular and humoral autoimmunity in the context of AIP.     

Protective CD8 memory T cell responses to mouse melanoma are generated in the absence of CD4 T cell help

Background

We have previously demonstrated that temporary depletion of CD4 T cells in mice with progressive B16 melanoma, followed by surgical tumor excision, induces protective memory CD8 T cell responses to melanoma/melanocyte antigens. We also showed that persistence of these CD8 T cells is supported, in an antigen-dependent fashion, by concurrent autoimmune melanocyte destruction. Herein we explore the requirement of CD4 T cell help in priming and maintaining this protective CD8 T cell response to melanoma.

Methodology and Principal Findings

To induce melanoma/melanocyte antigen-specific CD8 T cells, B16 tumor bearing mice were depleted of regulatory T cells (T_reg) by either temporary, or long-term continuous treatment with anti-CD4 (mAb clone GK1.5). Total depletion of CD4 T cells led to significant priming of IFN-γ-producing CD8 T cell responses to TRP-2 and gp100. Surprisingly, treatment with anti-CD25 (mAb clone PC61), to specifically deplete T_reg cells while leaving help intact, was ineffective at priming CD8 T cells. Thirty to sixty days after primary tumors were surgically excised, mice completely lacking CD4 T cell help developed autoimmune vitiligo, and maintained antigen-specific memory CD8 T cell responses that were highly effective at producing cytokines (IFN-γ, TNF-α, and IL-2). Mice lacking total CD4 T cell help also mounted protection against re-challenge with B16 melanoma sixty days after primary tumor excision.

Conclusions and Significance

This work establishes that CD4 T cell help is dispensable for the generation of protective memory T cell responses to melanoma. Our findings support further use of CD4 T cell depletion therapy for inducing long-lived immunity to cancer.     

The IgG2a antibody response to thyroglobulin is linked to the Igh locus in mouse

The IgG-subclass usage by several strains of mice in the response to immunization with mouse thyroglobulin (mTg) was examined in the experimental autoimmune thyroiditis model. While the subclass usage by most mouse strains was similar, the Igh^b allotype-bearing mice consistently produced lower IgG2a levels to mTg. Using CBA-Igh ^b congenic and recombinant inbred strains of mice, the lower level of IgG2a in the Igh^b mouse was mapped to the Igh locus. The regulation of IgG2a appeared to be cis controlled, as the CBA x C57BL/6F₁ mouse also produced reduced IgG2a of the Igh^b (B6) allotype but not Igh^j (CBA) allotype.     

Reaginic antibody formation in the mouse. VI. Suppression of IgE and IgG antibody responses to ovalbumin following the administration of high dose urea-denatured antigen.

The major antigenic determinants in ovalbumin molecules (OA) were lost following denaturation in 8 M urea. The urea-denatured antigen (UD-OA) failed to combine with anti-OA antibody, but was capable of priming mouse T cells specific for OA. BDF₁ mice primed with alum-precipitated OA were given three intravenous injections of 100 μg UD-OA at 3, 5, and 7 days after the primary immunization. The treatment with UD-OA suppressed both IgE and IgG antibody responses to OA. The same treatment of OA-primed animals with intravenous injections of OA resulted in suppression of IgE antibody response but enhanced IgG antibody response. Intravenous injections of either OA or UD-OA suppressed both IgE and IgG anti-DNP antibody responses of DNP-OA-primed animals but failed to suppress anti-hapten antibody responses to DNP-keyhole limpet hemocyanin. The effect of the treatment on helper T cells and B memory cells in OA-primed animals was studied by adoptive transfer experiments. The results showed that the OA-treatment as well as UD-OA-treatment suppressed the development of both helper function of T cells and B memory cells in the spleen, but the UD-OA treatment was more effective than OA-treatment for the suppression of B cell development. Possible mechanisms for the suppression of the development of immunocompetent cells were discussed.     

Induction and Role of Indoleamine 2,3 Dioxygenase in Mouse Models of Influenza A Virus Infection

Influenza infection stimulates protective host immune responses but paradoxically enhances lung indoleamine 2,3 dioxygenase (IDO) activity, an enzyme that suppresses helper/effector T cells and activates Foxp3-lineage regulatory CD4 T cells (Tregs). Influenza A/PR/8/34 (PR8) infection stimulated rapid elevation of IDO activity in lungs and lung-draining mediastinal lymph nodes (msLNs). Mice lacking intact IDO1 genes (IDO1-KO mice) exhibited significantly lower morbidity after sub-lethal PR8 infection, and genetic or pharmacologic IDO ablation led to much faster recovery after virus clearance. More robust influenza-specific effector CD8 T cell responses manifested in lungs of PR8-infected IDO1-KO mice, though virus clearance rates were unaffected by IDO ablation. Similar outcomes manifested in mice infected with a less virulent influenza A strain (X31). IDO induction in X31-infected lungs was dependent on IFN type II (IFNγ) signaling and was restricted to non-hematopoietic cells, while redundant IFN type 1 or type II signaling induced IDO exclusively in hematopoietic cells from msLNs. Memory T cells generated in X31-primed IDO1-KO mice protected mice from subsequent challenge with lethal doses of PR8 (100×LD₅₀). However recall T cell responses were less robust in lung interstitial tissues, and classic dominance of TCR Vβ8.3 chain usage amongst memory CD8⁺ T cells specific for influenza nucleoprotein (NP₃₆₆) did not manifest in IDO1-KO mice. Thus, influenza induced IDO activity in lungs enhanced morbidity, slowed recovery, restrained effector T cell responses in lungs and shaped memory T cell repertoire generation, but did not attenuate virus clearance during primary influenza A infection.