The sensitivity of IL-4 production for cAMP inducers is lost in CD4+ T cells from aged mice

CD4⁺ T cell clones have been demonstrated to display a differentialsensitivity for the induction of cAMP. In the present studywe investigated whether the differential sensitivity of CD4⁺T cell clones for cAMP inducers is also applicable to freshlyisolated phenotypically and functionally distinct CD4⁺ T cellsubsets that develop naturally in aging mice. Our results showthat the concanavalin A induced and anti-CD3 induced proliferativeresponse of CD4⁺ T cells from young mice is more sensitive forprostaglandin E₂ (PGE₂) and forskolin than that of their agedcounterparts, although the IL-2 production by these cells wasequally sensitive. In contrast, only a slight or no inhibitoryeffect of these cAMP inducers was found when the cells werestimulated with the combination of phorbol myristate acetateand lonomycln. In contrast to the findings obtained with T_n2clones, IL-4 production by freshly isolated CD4⁺ T cells wasinhibited by the cAMP inducers, whereas exogenous IL-2 had norestorative effect. However, the IL-4 production by CD4⁺ T cellsfrom aged mice was less sensitive than the IL-4 production byCD4⁺ T cells from young mice, although CD4⁺ T cells from agedmice showed significantly higher levels of intracellular cAMPin response to PGE₂. These higher levels of cAMP were relatedto the increased fraction of memory cells in aged mice: theMel-14^– Pgp-1⁺⁺ CD4⁺ T cells responded with at least 2-foldhigher levels of intracellular cAMP than the naive cells inyoung as well as in aged mice. Although memory CD4⁺ T cellsfrom young as well as aged mice responded vigorously to PGE₂by an enhancement of intracellular cAMP, only the IL-4 productionby cells from young mice was significantly inhibited. Therefore,it is not likely that the induction of cAMP is a major eventin the skewing of a primary response towards a T_h2 type of response.     

Anergy in vivo: down-regulation of antigen-specific CD4+ Th1 but not Th2 cytokine responses

Efficient immunologic tolerance, defined as antlgen-speclflcunresponslveness, can be peripherally induced by the l.v. Injectionof syngenelc splenocytes coupled with antigen using ethylenecarbodilmlde (ECDI). We have previously reported that unresponslvenessinduced via l.v. Injection of syngenelc splenocytes coupledwith intact, UV-lnactlvated Theiler's murine encephalomyelitisvirus (TMEV-SP) resulted in ‘split tolerance’. Bothvtrus-speclflc delayed-type hypersensltlvlty and lgG2a levelswere inhibited, whereas lgG1 levels were increased when comparedwith sham tolerized controls. In the present report we demonstratethat tolerance induced by l.v. Injection of TMEV-coupled splenocytesresulted in antigen-specific inhibition of T cell proliferation,as well as IL-2 and IFN- production in response to both wholeTMEV and the immunodomlnant viral epitope. Additionally, toleranceinduction resulted in abrogation of T_h1 -derived [IL-2, IFN-and LT/tumor necrosis factor-ß (TNF-ß)]cytokine mRNA expression in response to In vitro stimulationwith UV-inactlvated TMEV as determined by reverse transcrlptasepolymerase chain reaction. In contrast, expression of T_h2-derived(IL-4, IL-6 and IL-10) cytokine mRNA was not affected in tolerizedmice. Tolerance functioned directly at the level of CD4⁺ T_h1cells at both the induction and effector limbs as depletionof CD8⁺ T cells both prior to in vivo tolerizatlon or in vitroculture had no effect on inhibition of T_h1-specific responses.The mechanism of In vivo tolerance induction appeared to beanergy of CD4⁺ T_h1 cells since IL-2, IFN- and LT/TNF-ßmRNA expression as well as virus-specific prollferatlve responsescould be restored by addition of rlL-2 to In vitro culturesof tolerant, CD4⁺ T_h1 populations. These results suggest thatin vivo ‘split tolerance’ Induced by l.v. Injectionof ECDI-flxed, antigen-coupled splenocytes involves anergy ofTMEV-speclflc, CD4⁺ T_h1 lymphocytes and concomitant primingof T_h2 cells. The induction of antlgen-speclflc, in vivo anergyhas important implications in the design of therapeutic strategiesfor immunopathologic diseases mediated by T_h1 lymphocytes, especiallyT cell-mediated autoimmune disorders.     

Differentiation of human single-positive fetal thymocytes in vitro into IL-4- and/or IFN-{gamma}-producing CD4+ and CD8+ T cells

In this study we have investigated the capacity of human fetalthymocytes to differentiate in vitro into subsets of T cellswith polarized T_h1 or T_h2 cytokine profiles. Stimulation offreshly isolated human fetal thymocytes with anti-CD3 mAb, cross-linkedonto CD32,CD58,CD80-expressing mouse fibroblasts and subsequentculture in the presence of exogenous rIL-2 for 6 days, inducedthe production of both IL-4 and IFN-, which was mainly producedby CD4⁺ single-positive (SP) and CD8⁺ SP cells respectively.Addition of rIL-4 during priming augmented IL-4 production incultures of human fetal thymocytes, which was mainly due toan increased production of IL-4 by CD8SP cells. In contrast,addition of IL-4 to the cultures only slightly enhanced IL-4production and had little effect on frequencies of IL-4-producingCD4SP cells. Both CD4SP and CD8SP cells produced IL-5, IL-10and IL-13 at comparable levels, following priming in the presenceof rIL-4. Priming in the presence of rIL-12 strongly enhancedthe production of IFN- in both CD4SP and CD8SP cells. No correlationbetween expression of CD27, CD30 and CD60, and a particularcytokine profile of differentiated thymocytes could be demonstrated.Together, these results demonstrate the full capacity of fetalhuman thymocytes to differentiate into cytokine-producing Tcells in a priming milieu with appropriate stimulatory moleculesand exogenous cytokines. In addition, CD4SP thymocytes rapidlydifferentiate into polarized T_h2 cells following stimulationin vitro in the absence of exogenous rIL-4.     

Functional CD4+T cell subsets defined by expression of CD45RC and NTA260 antigens and age-associated polarization in murine lupus

Using two mAb, one specific to the alternative exon 6-dependentepitope of CD45 molecules(JH6.2) and one a natural thymocytotoxicautoantibody (NTA) with an unknown reactive epitope (NTA260),we subdivided splenic CD4⁺ T cells from 2-month-old BALB/c miceinto five phenotypically distinct subsets. CD45RC⁺NTA260^–(SI) cells were phenotypically analogous to CD4⁺ T cells predominatingin newborn mice and produced a significant amount of IL-2, butnot so IL-4, IL-10 or IFN- when stimulated with immobilizedanti-CD3 mAb in vitro. They appeared to consist mainly of naiveT_hP cells. The CD45RC⁺;NTA260⁺ (S II) subset also produced IL-2,but not other cytokines; however, the IL-2 levels produced weremuch higher than seen with the S I subset, thereby suggestingthe predominance of further maturated T_hP cells. The D45RC^–NTA260⁺(S III) subset mainly produced IL-4, IL-10, IFN- and less IL-2,and contained memory cells that helped the secondary antibodyresponse to a recall antigen, and hence contained T_h2 and probablya mixture of T_h0 and T_h1 cells. The CD45RC^–NTA260^–(S IV) subset was a poor responder to the immobilized anti-CD3mAb. The CD45RC^brightNTA260^dull(S V) subset consisted of a smallnumber of cells that were phenotypically analogous to activatedCD4⁺ T cells. While an age-associated decrease in the proportionof S I and less markedly in S II and in turn increase in S IIIsubsets of CD4⁺ T cells occurred in normal BALB/c mice, autoimmunedisease-prone (NZBxNZW)F₁ mice showed a marked age-associateddecrease in the proportion of not only S I, II but also IIIsubsets. As aged (NZBxNZW)F₁ mice carry CD4⁺ T helper cellsfor IgG anti-DNA antibody production, such age-associated polarizationto the S IV subset appears to be critical in the pathogeneslsof autoimmune disease in these mice.     

Brucella abortus induces a novel cytokine gene expression pattern characterized by elevated IL-10 and IFN-{gamma} in CD4+ T cells

Immunization of BALB/c mice with killed Brucella abortus (BA)has previously been shown to Increase serum lgG2a levels andlong-term T cell clones from these mice secrete T_h1-associatedcytokines: IFN- and IL-2 but not IL-4 or IL-5. We analyzed cytokinegene expression following primary immunization with BA to determinewhen CD4⁺ T cells first express cytokine genes and whether specifichypothesized cytokine patterns (e.g. T_h precursor, T_h0) couldbe identified prior to a T_h1-like pattern. Our results demonstrateda highly consistent and novel pattern of T_h 1/T_h2 cytokine geneexpression characterized by elevated IL-10 and IFN- in CD4⁺T cells which rapidly manifests itself and is sustained forat least 10 days after immunization. No elevation in IL-2 cytokinegene expression was observed and treatment of BA-immunlzed micewith blocking anti- IL-2 antibodies had no effect on the cytokinegene expression pattern, although treatment with anti-IFN antibodiesresulted in increased IL-4, IL-5, and IL-9 cytoklne gene expression,In the absence of any change In IFN- or IL-10 as early as 4days after immunization. These results suggest that a wholepathogen may trigger sufficient costimulatory signals to rapidlyinduce effector T cells in the absence of elevated IL-2 andthat IL-10 Is specifically elevated in certain T_h1-like responses.     

Frequencies of CD4+ T cells reactive with Plasmodium chabaudi chabaudi: distinct response kinetics for cells with Th1 and Th2 characteristics during infection

The functional heterogeneity of the CD4⁺ T cell response toPlasmodium chabaudi has been evaluated. Using a limiting dilutionassay system and a variety of assays to detect -interferon (IFN-),interleukln-2 (IL-2), IL-3, and T helper (T_h) cells for malaria-specificantibody production, the precursor frequencies of P. chabaudl-reactiveT cells have been calculated. The patterns of lymphokines producedby individual microcultures of the limiting dilution assay generallysupported the Idea of two functionally distinct CD4⁺ subsets:one which produces IFN- and IL-2 (T_h1) and one which Is an effectivehelper cell for antibody production (T_h2) However, it couldnot be determined whether the overiapping functions observedin some cultures represented T cells which could produce allfactors or separate clones which were developing In the samewells. During the first 14 days of an erythrocytic Infectionof P. chabaudi the predominant T cell response was of the T_h1-tupe.The frequency of these cells decreased after 14 days. By 3 weeksafter Infection the CD4⁺ T cell response was characterized byT_h2 cells, as defined by their ability to act as helper cellsin the production of malaria-specific antibody. These data supportthe hypothesis that early clearance of P. chabaudi may be antibody-Independentbut that the final clearance mechanism coincides with the appearanceof helper cells and antibody.     

CD44 plays a co-stimulatory role in murine T cell activation: ligation of CD44 selectively co-stimulates IL-2 production, but not proliferation in TCR-stimulated murine Th1 cells

The murine CD44 receptor family is thought to be involved ina variety of lymphocyte functions, including lymphopoesis, lymphocytehoming and cell migration. Herein, we show that murine CD44also plays a role as a co-stimulatory molecule for the activationof CD4⁺ T cells. Ligation of CD44 by mAb enhanced IL-2 productionof long-term cultured, anti-CD3-stimulated T_h1 cell lines. Moreover,anti-CD44 mAb synergized with anti-CD28 mAb in exerting thiseffect. A synergism of anti-CD28 and anti-CD44 mAb to co-stimulateIL-2 production was also observed in anti-CD3- triggered, freshlyisolated splenic CD4⁺ T cells. Blocking experiments with cyclosporinA indicated that the intracellular pathways used by the CD28and CD44 molecules appear to be different. In contrast to theeffects on the IL-2 production of T_h1 cells, neither anti-CD44mAb alone nor the combination of anti-CD44 with anti-CD28 wereable to induce proliferation of anti-CD3-triggered T_h1 cells.In accordance, triggering of CD44 and/or CD28 by mAb was notsufficient to reverse the previously described ‘proliferativeblock’. This term describes the unresponsiveness of T_h1cells against IL-2, which occurs when T_h1 cells are triggeredby anti-CD3 in the absence of co-signals. These data lead usto propose a model of T_h1 cell activation which includes twofunctionally different types of co-signals: one for IL-2 productionand a separate one for proliferation.     

Specific decrease of Th1-like activity in mice with plasma cell tumors

Previously we examined the ability of the host's immune responsesto regulate Ig production in an IgE-secreting murine plasmacell tumor (B53). In the present study we have examined thereverse phenomenon, in that we have investigated the effectsof this and other plasma cell tumors on the immune responsesof their hosts. We found that splenocytes from plasma cell tumor-bearingmice demonstrate decreased proliferation in response to polyclonalstimulation by either Con A or a combination of PMA and calciumionophore (A23187 [GenBank] ). Fractionation of the splenocytes demonstratedthat this reduction in proliferation was confined to CD4⁺T cellsand that the proliferation of CD8⁺ T cells was unaffected. Inorder to determine whether the down-modulatory effects of thetumor were confined to a particular CD4⁺helper T cell subset,we examined the production of cytokines representing the T_h1subset (IL-2 and IFN-) and the T_h2 subset (IL-4 and IL-10) fromstimulated splenocytes and from stimulated enriched splenicT cells. We found that both stimulated splenocytes and T cellsfrom plasma cell tumor-bearing mice produced lower levels ofthe T_h1 cytokines IL-2 and IFN- compared with normal cultures,demonstrating that T_h1-like responses are inhibitsed in thehosts of these tumors. However, no alterations in the productionof the T_h2 cytokines IL-4 and IL-10 were observed in these stimulatedsplenocyte or T cell cultures from the tumor-bearing mice. Thus,our data demonstrate that plasma cell tumors induce a decreasein the immune responsiveness of their hosts, and this decreaseis restricted specifically to T_h1-like activity, with the T_h2-likeactivity and CD8⁺T cell proliferative responses remaining intact.     

Selective accumulation of CCR5+ T lymphocytes into inflamed joints of rheumatoid arthritis

Chemokines and their receptors play critical roles in the selectiverecruitment of various subsets of leukocytes. Recent studieshave indicated that some chemokine receptors are differentiallyexpressed on T_h1 and T_h2 cells. However, available data concerningthe presence of T cells with a T_h1 or a T_h2 character and theexpression of chemokine receptors on infiltrating T cells inthe rheumatic joint are still limited. In this study, we investigatedthe expression of CC chemokine receptor 4 (CCR4) and CCR5, whichhave been shown to be preferentially expressed on T_h2 and T_h1respectively on T cells from rheumatoid arthritis (RA) patients.Although both CCR5⁺ and CCR4⁺ CD4⁺ T cell populations were observedin peripheral blood mononuclear cells from healthy controlsand osteoarthritis patients, these cell populations were decreasedin patients with active RA. In contrast, the vast majority ofsynovial fluid (SF) T cells from active RA patients expressedCCR5 but not CCR4. CCR5 ligands, MIP-1 and RANTES, were foundin RA SF at high levels. CCR5⁺ CD4⁺ T cells from SF mononuclearcells of RA patients produced IFN- but not IL-4 in responseto anti-CD3 stimulation in vitro. These results indicated thatdifferential expression of chemokine receptors plays a criticalrole for selective recruitment of pro-inflammatory T cells intothe joints of RA.     

Co-activation of naive CD4+ T cells and bone marrow-derived mast cells results in the development of Th2 cells

Activation of nalve dense CD4⁺ T cells by plate-bound anti-CD3antibodies favors the development of T_h1 cells which, upon re-stimulation,produce significant amounts of INF- but no IL-4. However, co-activationof such naive T cells in the presence of IgE [anti-dlnitrophenyl(DNP)]-loaded bone marrow-derived mast cells (BMMC) on platescoated with anti-CD3 antibodies and DNP-BSA led to the developmentof IL-4-produclng T_h2 cells. The same result could be observedif irradiated (800 rad) BMMC were applied as co-stimulators.Moreover, BMMC could be replaced by the supernatant of IgE-activatedBMMC suggesting that a soluble mediator, presumably IL-4, wasresponsible for this effect. This assumption was substantiatedusing neutralizing anti-IL-4 antibodies which abolished theBMMC-medlated T_h2 development in all cases. Addition of IL-12,a cytokine that was shown to antagonize the T_h2-promoting effectof IL-4 in vivo, could not inhibit the development of IL-4-producingT cells, but gave rise to a T cell population which producedrelatively high amounts of IL-4 and IFN-. Since BMMC representthe in vitro equivalent of mucosai mast cells these data suggestthat IgE-activated mucosai mast cells can bias an emerging Tcell dependent Immune response towards a T_h2 dominated reactionby the initial production of IL-4.     

CD4+Thy1- thymocytes with a Th-type 2 cytokine response

We have identified a small subset of CD3⁺, CD4⁺, CD8^–thymocytes that do not express Thy1 (CD90). This Thy1^–subset represents 1–3.7% of the total number of thymocytesin a naive mouse. CD4⁺Thy1^– thymocytes express high levelsof CD3, intermediate to high levels of heat-stable antigen (HSA),and low levels of CD25, CD45RB, CD69, CD44 and CD62L. They producehigh titers of IL-4 and no IFN- upon stimulation in vitro, aresponse characteristic of T_h2 cells. In the thymi of mice infectedneonatally with a high dose of the retrovirus Cas-Br-E MuLV,the frequency of CD4⁺Thy1^– cells increased ~10-fold. High-dosevirus infection resulted in decreased HSA and increased CD44expression on CD4⁺Thy1^– cells relative to cells from naivemice. CD4⁺Thy1^– cells from high-dose infected mice alsosecreted IL-4 and not IFN- upon in vitro stimulation. We previouslyreported that infection of newborn mice with a high dose ofmurine retrovirus results in the induction of a non-protectiveanti-viral T_h2 T cell response; CD4⁺Thy1^– thymocytes witha T_h2-like cytokine profile may play a role in determining thecytokine bias of this anti-viral response.     

CD28 ligands CD80 (B7-1) and CD86 (B7-2) induce long-term autocrine growth of CD4+ T cells and induce similar patterns of cytokine secretion in vitro

The interaction of CD28 and its ligands is critical for antigen-inducedT cell activation. Recent studies have demonstrated the existenceof at least two members of the B7 receptor family. In this report,the co-stimulatory signals provided by CD80 (B7-1) or CD86 (B7-2)were compared to CD28 ligation by mAb. We demonstrate that thekinetics of induction of T cell proliferation after anti-CD3stimulation was similar regardless of the form of co-stimulation.Similarly, B7-1 and B7-2 could both maintain long-term expansionof CD4 cells. The co-stimulatory effects of both B7-1 and B7-2were dependent on CD28 cross-linking, based on complete inhibitionof proliferation by CD28 antibody Fab fragments. Co-stimulationwith B7-1 and B7-2 induced high levels of cytokine secretionby resting T cells, and the effects of B7-1 and B7-2 could notbe distinguished. This conclusion is based on analysis of theinitial activation of CD28⁺ T cells. as well as T cell subpopulationsconsisting of CD4⁺ and CD8⁺ T cells. Both B7-1 and B7-2 couldelicit IL-4 secretion from CD4⁺ T cells while anti-CD28 antibodyinduced substantially less IL-4 secretion. Furthermore, bothB7-1 and B7-2 could stimulate high levels of IFN- and IL-4 fromCD4⁺CD45RO⁺ cells, while neither B7 receptor could co-stimulateIFN- and IL-4 secretion from CD4⁺CD45RA⁺ T cells. B7-1 and B7-2could, however, co-stimulate CD4⁺CD45RA⁺ T cells to secreteIL-2. By contrast, when previously activated T cells were tested,re-stimulation of CD4⁺ T cell blasts with B7-1 or B7-2 resultedin higher secretion of IL-4 and IL-5 than anti-CD28, while re-stimulationwith anti-CD28 antibody maintained a higher level of secretionof IL-2 and IFN- than B7-1 or B7-2. These observations may haveimportant implications because they suggest that the mannerof CD28 ligation can be a critical determinant in the developmentof cytokine secretion that corresponds to T_h1- and T_h2-likepatterns of differentiation. Together these observations suggestthat there are no Intrinsic differences between B7-1 and B7-2in their ability to co-stimulate the populations of cells thatwe have tested.     

The relative contribution of IL-4 and IL-13 to human IgE synthesis induced by activated CD4 or CD8 T cells

The relative contribution of IL-4 and IL-13 to the regulation of IgE synthesis has remained relatively poorly characterized, partially because of lack of suitable animal models. We have studied the roles of IL-4 and IL-13 in human IgE synthesis induced by supernatants derived from activated CD4⁺⁺ or CD8⁺ T cell clones. Neutralizing anti–IL-4 and anti–IL-13 monoclonal antibodies (mAbs) inhibited IgE synthesis induced by anti-CD40 mAbs and supernatants from CD4⁺ T cells by an average 61% and 42%, respectively (n = 25). Recombinant IL-13 had additive effects on IL-4-induced IgE synthesis, but only when IL-4 was present at low concentrations. Accordingly, IL-4 was the dominant IgE synthesis–inducing cytokine derived from highly polarized T helper (TH)₂ cells. However, anti–IL-13 mAbs also significantly inhibited IgE synthesis induced by two of three supernatants derived from allergen-specific T_H2-like cell lines generated from the skin of patients with atopic dermatitis. Furthermore, anti–IL-13 mAbs almost completely inhibited IgE synthesis induced by supernatants from T_H1 cells or CD8⁺ T cell clones. Taken together, these data indicate that IL-13, in addition to IL-4, contributes to IgE synthesis induced by all T helper cell subsets, including allergen-specific T_H2 cells. Moreover, IL-13 appears to be the major IgE synthesis–inducing cytokine derived from T_H1 cells or CD8⁺ T cells. (J Allergy Clin Immunol 1997;100:792-801.)     

Polyclonal activation of immature B cells by preactivated T cells: the role of IL-4 and CD40 ligand

It is well-established that preactivated CD4⁺ T cells can activatemature B cells in a polyclonal, MHC-unrestricted fashion. Wehave used this system to investigate the effects of T cell-derivedsignals on immature B cells purified from the spleens of neonatalmice, since these cells are unresponsive to many polyclonalactivators and are exquisitely sensitive to tolerizatlon. Weshow that immature B cells can be induced to proliferate byanti-CD3 activated, fixed T_h1 and T_h2 cells, although the latterinduce a greater response than the former. Antibodies to IL-4partially blocked stimulation by T_h2 cells, where as antibodiesto IL-2 and IL-5 had no effect on responses to T_h1 cells. Thissuggested that molecules in addition to IL-4 contribute to thecapacity of T cells to induce B cell activation, one likelycandidate being the ligand for CD40. We therefore generatedmouse erythroleukemia (MEL) transfectants which express CD40ligand (CD40L). These transfectants also induced proliferationof immature B cells, which is enhanced by IL-;4. Unlike thesituation with mature B cells, both anti-µ and anti- antibodiesinhibited the activation of immature B cells by CD40L-MEL cells.However, this inhibition was reversed by IL-4, which synergizedwith signals delivered through CD40 to render immature B cellsrefractory to negative signals delivered through slg. Takentogether these data suggest that immature B cells can be activatedby T cell-derived contact signals and that CD40L – CD40interactions, in the presence of IL-4, are capable of abrogatingthe negative signals generated via slgM and slgD receptors expressedby these cells.     

Altered response of CD4+ T cell subsets to Plasmodium chabaudi chabaudi in B cell-deficient mice

Mice depleted of B cells from birth by treatment with anti-_µantibodies can control but not clear an infection with the malariaparasite Plasmodium chabaudi chabaudi (AS). Splenic CD4⁺ T cellsfrom these mice were unable to mount a significant T_h2 responseto the parasite in vitro as shown by much lower precursor frequenciesof T_h cells for antibody production and of IL-4-producing cellscompared with the response of control-treated mice. CD4⁺ T cellsof the anti-_µ-treated mice which respond to antigens ofP. chabaudi chabaudi maintained a T_h1 phenotype throughout primaryinfection, in contrast to control mice in which a sequentialappearance of T_h1 and T_h2 responses was observed. These datashow that T_h1 responses in anti-_µ-treated mice are sufficientto control parasitemia but not to eliminate an infection. Thedata further suggest that depletion of B cells by treatmentwith anti-_µ; antibodies reduces the generation of theT_h2 subset during a primary response to P. chabaudi chabaudi.     

Impaired CD28-mediated co-stimulation in anergic T cells

We have investigated a CD28 co-stimulation in anergic T cellsin staphylococcal enterotoxin Binoculated mice by stimulatingthe cells with a plate-coated anti-TCR antibody in the presenceor absence of an anti-CD28 antibody. CD28 co-stimulation increasedthe levels of IL-2 and IL-4 mRNAs in nalve CD4⁺V_ß8⁺T cells. However, it did not increase the levels of IL-4 mRNAat all and only partially increased those of IL-2 mRNA in anergicT cells. It was demonstrated that CD28 co-stimulation was impairedso that it no longer stabilized cytoklne mRNAs in anergic cells.The levels of IL-4 mRNA in response to TCR stimulation werehigher in anergic T cells than those in nalve T cells in spiteof the defective CD28 co-stimulation in the former cells. Anergyinduction and generation of a T_h2-type immune response in vivoare discussed     

T cell subpopulation phenotypes in filarial infections: CD27 negativity defines a population greatly enriched for Th2 cells

Three-color flow cytometric analysis was used to define surfacemarkers which identify the T_h2-type CD4⁺ cells responsible forthe eosinophilia and elevated serum IgE typical of tissue invasivehelminth infections. A group of six mAba to well known cellsurface markers were screened for differential expression onCD4⁺ CD45RO⁺ lymphocytes from normal individuals (NL; n = 6)and filaria-infected patients (PT; n = 10). The majority ofmarkers were expressed equally by both groups, but the CD4⁺CD45RO⁺ cells in the PTs showed significantly higher levelsof expression of HLA-DR than those of NLs (P = 0.014). ThisCD4⁺ HLA-DR⁺ subpopulation was then studied further for itsexpression of an additional 10 activation and adhesion molecules.CD27 showed a trend for lower intensities of expression on PTCD4⁺ HLA-DR⁺ cells than on those of NLs. Analysis of the serumfrom both NLs and PTs revealed that PTs had significantly higherlevels of soluble CD27 and CD25 (IL-2R) In the serum than NLs(P < 0.01 and P = 0.022 respectively) indicating a generalstate of Immune activation and differentiation. Functional analysisof the CD4⁺ HLA-DR⁺ and the CD4⁺ CD27^– subpopulatlonsrevealed that the CD4⁺ HLA-DR⁺ cells produced significantlyhigher levels of IL-5 than the CD4⁺ HLA-DR^– cells (P <0.04), and the CD4⁺ CD27^– cells produced significantlyhigher levels of both IL-4 and IL-5 than the CD4⁺ CD27^–cells (P <0.05 and P <0.001 respectively). Thus, whilethe CD4⁺ CD27^– and CD27⁺ subpopulatlons contain T_h1 andT_h0 cells, only the CD4⁺ CD27^– population contains theT_h2 cells (producing both IL-4 and IL-5).