Optimal strategies to identify aberrant intra-epithelial lymphocytes in refractory coeliac disease.

INTRODUCTION: Different strategies have been developed to identify those refractory celiac disease (RCD) patients who are at risk to develop an enteropathy associated T-cell lymphoma (EATL). Flow cytometric analysis of intra-epithelial lymphocytes (IEL) with an aberrant phenotype is considered the golden standard but is not widely available. Immunohistochemistry (IHC) and T-cell receptor (TCR) rearrangement studies are commonly available but may lack sensitivity and specificity. Here, we compared the three different methods in the workup of patients suspected for RCD. METHODS: Duodenal biopsies from control patient (n = 5), RCD patients with moderately increased aberrant IEL populations (20-50 %: n = 14), and RCD patients with high numbers of aberrant IEL (>50 %: n = 5) as determined by flow cytometry were analysed by IHC and TCR-γ chain rearrangement analysis. Three pathologists scored the slides independently. RESULTS: Sensitivity of IHC and TCR-γ rearrangement analysis in RCD patients with high numbers of aberrant IELs was 100 and 71 %, respectively. RCD patients with aberrant cells between 25 and 50 % however, were missed by IHC and TCR in 50 and 57 % of cases, respectively. In addition, inter-rater reliability analysis of the IHC scoring revealed coder-pair Kappa coefficients between 0.28 and 0.85. CONCLUSION: Immunohistochemistry and to a lesser extent TCR-γ clonality analysis are sensitive in identifying patients with high numbers of aberrant IEL populations, yet miss half of RCD patients with moderately increased numbers. In addition, IHC has a high inter-observer variability. Therefore, patients suspected for RCD should undergo flow cytometric analysis of the duodenum.

Serum autoantibodies directed against transglutaminase-2 have a low avidity compared with alloantibodies against gliadin in coeliac disease.

Coeliac disease is characterized by intolerance to gliadin and related gluten components present in wheat, barley and rye. Coeliac disease patients harbour antibodies directed against alloantigens such as gliadin, but also against the autoantigen transglutaminase-2 (TG2). The type and quality of antibody responses provides insight into the underlying immune activation processes. Therefore, in this study we have analysed the avidity of the antibody response directed against the autoantigen TG2 and compared this with antibody responses against the alloantigens gliadin and Escherichia coli. We observed that the immunoglobulin (Ig)A autoantibody response directed against TG2 is of low avidity compared with the IgA response against the alloantigens gliadin and E. coli in the same patients; the same was true for IgG, both in IgA-deficient and in -sufficient coeliac patients. The observed avidities appear not to be related to disease stage, antibody levels, age or duration of exposure to gluten. In conclusion, in coeliac disease there is a clear difference in avidity of the antibody responses directed against the auto- and alloantigens, indicating different regulation or site of initiation of these responses.

Effector memory T-cell frequencies in relation to tumour stage, location and HPV status in HNSCC patients.

BACKGROUND: The immune system plays an important role in tumour immune surveillance. Head and neck squamous cell carcinoma patients are often immune compromised. OBJECTIVE: To chart the baseline levels of T-cell subpopulation frequencies in patients with cancer prior to treatment. SUBJECTS AND METHODS: Blood samples of patients were taken at the time of diagnosis, analysed with flowcytometry and compared with blood samples of healthy donors. RESULTS: Compared to healthy donors, a significant shift from naive to effector memory T cells was observed. This effect was most prominent in stage II patients. A similar shift from naive to effector memory T cells was noted in patients with oropharynx or larynx squamous cell carcinomas. Furthermore, the percentage of effector memory and effector T cells was higher in the group of patients with human papillomavirus-positive oropharyngeal squamous cell carcinomas, compared with patients with human papillomavirus-negative tumours, suggestive of virus-induced T-cell activation. CONCLUSION: Here, we provide a simple and easily implementable tool to document T lymphocyte subsets in the peripheral blood of head and neck cancer patients, which might be useful for prognosis and/or therapy response prediction.

Palladium-induced Th2 cytokine responses reflect skin test reactivity.

Recently, a crucial role of Th2 responses in nickel allergic contact dermatitis (ACD) was demonstrated. As palladium allergy is an issue of growing interest, the diagnostic potential of Th2 parameters for palladium sensitization was investigated. Palladium (Na(2) [PdCl(4)])-induced lymphocyte proliferation (LPT), Th1 and Th2 cytokine production were correlated with skin test (ST) reactivity in 16 positive and 21 negative controls. Furthermore, the diagnostic potential of these assays was evaluated using receiver operating characteristics (ROC) analysis. For comparison, same experiments were carried out for nickel (NiSO(4)). Correlation coefficients between palladium ST reactivity and IFN-γ, LPT, IL-5, and IL-13 were 0.34, 0.51, 0.69, and 0.78, and overall test accuracies were 68%, 81%, 89%, and 95%, respectively. Both palladium- and nickel-mediated Th2 responses tightly correlate with ST reactivity, supporting recent findings on the crucial role of Th2 involvement in ACD. Therefore, these assays may have great potential as diagnostic tools for future in vitro sensitization testing.

The surgical stress response and postoperative immune function after laparoscopic or conventional total mesorectal excision in rectal cancer: a randomized trial.

PURPOSE: This study evaluated differences in stress response and immunological function following laparoscopic and conventional total mesorectal excision (TME) for rectal cancer. METHODS: Patients with non-metastasized rectal cancer were prospectively randomized to open (n = 18) or laparoscopic (n = 22) TME. Blood samples were taken preoperatively (baseline), 2, 24, and 72 h following surgery. Systemic white blood cell and monocyte count, C-reactive protein, interleukin-6 (IL-6), interleukin-8 (IL-8), HLA-DR expression on monocytes, growth hormone, prolactin, and cortisol were measured. RESULTS: Forty patients with a median age of 66 years (interquartile range, 60-74 years) were included. Eighteen patients (45%) were randomized to open surgery and 22 patients (55%) to laparoscopic surgery. Patient demographics in terms of gender, age, BMI, ASA classification, localization of the tumor, and type of neoadjuvant therapy were comparable for both groups. Laparoscopic surgery resulted in a significantly better short-term preservation of postoperative immune function. HLA-DR expression on monocytes was significantly higher (64% vs 50%, P = 0.014) and IL-6 level increase was significantly lower (4.6 vs 10.8, P = 0.003) 2 h after laparoscopic surgery. No differences between the open and laparoscopic technique were observed in postoperative white blood cell count, monocyte count, C-reactive protein, IL-8, growth hormone, prolactin, and cortisol levels. CONCLUSION: Short-term postoperative immune and inflammatory functions tended to be better after laparoscopic rectal surgery. However, the differences were not consistent at all time intervals, making a definitive conclusion difficult. Better preserved inflammatory function 2 h after surgery may reflect a reduction in operative trauma when the laparoscopic technique is compared with open rectal procedures.

Coeliac disease in China, a field waiting for exploration.

BACKGROUND: no systematic studies on the prevalence of coeliac disease (CD) have been reported from China. In western populations CD is more common in patients with insulin dependent diabetes mellitus (IDDM) and in diarrhoea-predominant irritable bowel syndrome (D-IBS). We have screened patients with these conditions presenting to the outpatient department of a large hospital of "Traditional Chinese Medicine" (TCM) in Nanjing, Jiangsu province, P.R. China. METHODS: we tested sera of 78 unrelated Han Chinese patients (5 IDDM and 73 D-IBS), using ELISA serological tests for IgG anti-gliadin antibodies (IgG-AGA) and IgA anti-tissue transglutaminase antibodies (IgA-tTG). RESULTS: six out of 78 patients (7.7%) were positive for IgG-AGA (two men and four women) and two (2.6%) were positive for IgA-tTGs. One of the latter patients was negative for IgG-AGA. Besides, one patient had a dubious IgA-tTG antibody and a positive IgG-AGA. None of the six patients agreed to undergo duodenal biopsy. Two out of these six patients followed a gluten-free diet for one year. In one patient the diarrhoea ceased and his body weight increased. Another stopped losing weight. CONCLUSIONS: this study previously published as a letter in GUT (Wu J, Xia B, von Blomberg BME, Zhao C, Yang XW, Crusius JBA, Peña AS. Coeliac disease: emerging in China? Gut 2010; 59(3): 418-9) demonstrated that CD may exist in the Jiangsu province of P.R. China. The present article draws attention to the difficulties of following a standard protocol in China such as established in western countries and highlights important factors less well known in the west in relation to the development of CD in China. Wheat production became significant in China between 1600 and 1300 B.C. After the Han dynasty (500-200 B.C.), wheat was one of the main cereals in China. One the major wheat fields in China is located in the Jiangsu province where the research for this article was performed. A review of Chinese literature shows that the predominant HLA-DQ CD risk alleles and haplotypes are present in the Jiangsu province. Genetic background, food consumption, and the results of our study suggest that CD should actively be investigated in P.R. China.

No evidence of misdiagnosis in patients with multiple sclerosis and repeated positive anticardiolipin antibody testing based on magnetic resonance imaging and long term follow-up.

OBJECTIVE: To determine whether patients with definite multiple sclerosis (MS) and repeated positive anticardiolipin antibody (aCL Ab) testing fulfil the recently updated criteria for the antiphospholipid syndrome (APS). Also, to determine if these patients form a separate subgroup in terms of long term follow-up and MRI characteristics. DESIGN: A blinded case control study comparing MRI patterns between aCL Ab positive and negative MS patients with a clinical follow-up of 7 years. PARTICIPANTS: 8 (5.6%; male:female ratio 2:6; 6 relapsing-remitting subtype, 1 primary progressive subtype and 1 neuromyelitis optica (NMO)) of 143 consecutive patients with definite MS or NMO (71% relapsing-remitting, 18% secondary progressive and 6% primary progressive disease course; 4% NMO) showed repeated positive aCL Ab testing. SETTING: Outpatient clinic of a tertiary MS centre in The Netherlands. RESULTS: All eight aCL Ab positive patients had levels below 40 MPL/GPL units, with the majority of intervals between tests of at least 12 weeks. After follow-up, none of the patients fulfilled the criteria for APS. No specific MRI features were present compared with 24 matched aCL Ab negative patients. CONCLUSIONS: No aCL Ab positive MS patient fulfilled the criteria for APS, arguing against a possible misdiagnosis or coexistence.

Outcome of Referrals for Non-Responsive Celiac Disease in a Tertiary Center: Low Incidence of Refractory Celiac Disease in the Netherlands.

OBJECTIVES: Refractory celiac disease (RCD) is a severe cause of non-responsive celiac disease (CD) due to its association with the enteropathy associated T-cell lymphoma (EATL). Conflicting data exist on the prevalence and the clinical manifestations of RCD type I (RCD I) and type II (RCD II). The aim of the current study was to provide insight in the incidence of RCD and in the distinction with other causes of non-responsive CD. METHODS: A total of 106 CD patients were referred to our tertiary referral center between January 2006 and December 2011 for evaluation of non-responsive CD. In addition, a questionnaire was sent to all 82 gastroenterology departments in the Netherlands to reveal whether a patient with RCD was currently being evaluated or had been treated between 2006 and 2012. RESULTS: During a 6 year period, a total of 31 patients were diagnosed with RCD (19 RCD I and 12 RCD II). The nationwide survey revealed 5 additional patients with RCD I and one patient with RCD II. This leads to an annual incidence of RCD of 0.83/10.000 CD patients. The remaining patients were diagnosed with involuntary gluten ingestion (21.7%), delayed mucosal recovery (11.3%), enteropathy associated T-cell lymphoma (7.5%) and autoimmune enteropathy (1.8%). CONCLUSIONS: This nationwide study reveals a low incidence of RCD in the Netherlands. Nevertheless, RCD is a clinically relevant disease entity in CD patients non-responsive to the gluten-free diet.

CXCL8 secretion by dendritic cells predicts contact allergens from irritants.

Monocyte-derived dendritic cell functions have been explored for identification of contact allergens in vitro. Current methods, including measurement of changes in cell surface marker expression (e.g. CD83, CD86) do not provide a sensitive method for detecting the sensitising potential of a chemical. In this study, we investigated whether chemokine production by monocyte-derived dendritic cells is increased upon maturation and whether chemokine production can provide methodology for the detection of allergens. Monocyte-derived dendritic cells were exposed to allergens (nickel sulphate, cobalt chloride, palladium chloride, copper sulphate, chrome-(III)-chloride, potassium dichromate, p-phenylenediamine and dinitrochlorobenzene) and irritants (sodium dodecyl sulphate, dimethylsulphoxide, benzalkoniumchloride and propane-1-ol). CD83 and CD86 expression was analysed by flow cytometry and chemokine production (CXCL8, CCL5, CCL17, CCL18, CCL19, CCL20, CCL22) was determined by ELISA. Significant up regulation of CD83 and CD86 expression could only be induced by three out of seven and five out of seven allergens, respectively. In contrast, CXCL8 production was significantly increased after stimulation with all allergens tested, whereas irritant exposure led to decreased CXCL8 production. All other chemokines tested, failed in identifying contact allergens. In conclusion, CXCL8 production, next to CD83 and CD86 up regulation, by monocyte-derived dendritic cells provides a promising in vitro tool for discrimination between allergens and irritants.

Innate stimulatory capacity of high molecular weight transition metals Au (gold) and Hg (mercury).

Nickel, cobalt and palladium ions can induce an innate immune response by triggering Toll-like receptor (TLR)-4 which is present on dendritic cells (DC). Here we studied mechanisms of action for DC immunotoxicity to gold and mercury. Next to gold (Na3Au (S2O3)2⋅2H2O) and mercury (HgCl2), nickel (NiCl2) was included as a positive control. MoDC activation was assessed by release of the pro-inflammatory mediator IL-8. Also PBMC were studied, and THP-1 cells were used as a substitution for DC for evaluation of cytokines and chemokines, as well as phenotypic, alterations in response to gold and mercury. Our results showed that both Na3Au (S2O3)2⋅2H2O and HgCl2 induce substantial release of IL-8, but not IL-6, CCL2 or IL-10, from MoDc, PBMC, or THP-1 cells. Also gold and, to a lesser extent mercury, caused modest dendritic cell maturation as detected by increased membrane expression of CD40 and CD80. Both metals thus show innate immune response capacities, although to a lower extent than reported earlier for NiCl2, CoCl2 and Na2 [PdCl4]. Importantly, the gold-induced response could be ascribed to TLR3 rather than TLR4 triggering, whereas the nature of the innate mercury response remains to be clarified. In conclusion both gold and mercury can induce innate immune responses, which for gold could be ascribed to TLR3 dependent signalling. These responses are likely to contribute to adaptive immune responses to these metals, as reflected by skin and mucosal allergies.

Non-sensitizing epicutaneous skin tests prevent subsequent induction of immune tolerance.

Oral administration of nickel or chromium to naive guinea pigs results in immune unresponsiveness to subsequent induction of allergic contact hypersensitivity. Such "oral tolerance" depends on the oral dose, is antigen specific, T-suppressor-cell mediated, and very persistent. In contrast, oral antigen administration to sensitized animals results at best in transient desensitization. Here we report that even non-sensitizing epicutaneous skin contacts prevented the subsequent induction of oral tolerance. These data support the view that primed T cells are less sensitive to suppressor T-cell function than naive T cells.

In vivo effects of sex steroids on lymphocyte responsiveness and immunoglobulin levels in humans.

The female predominance in several autoimmune diseases suggests a role for sex steroid hormones in disease susceptibility. We therefore investigated to what extent sex hormones would influence immune responsiveness. We analyzed T helper type 1 (TH1) and type 2 cytokine patterns, chemokine receptor expression (n = 2 x 10), and Ig levels (n = 2 x 25) in transsexual men and women before and after 4 months of cross-sex hormone administration. Antithyroperoxidase levels were compared between 186 transsexual males (treated >5 yr with estrogens) and 186 male controls. In men, estrogens plus antiandrogens increased free cortisol levels in 24-h urine samples, decreased natural killer cell numbers, and slightly inhibited the mitogen-induced interferon-gamma/interleukin-4 ratio, but up-regulated the expression of TH1-associated chemokine receptors, CCR1, CXCR3, and CCR5. Conversely, in women, androgens slightly decreased free cortisol levels in 24-h urine samples and enhanced the mitogen-induced interferon-gamma/interleukin-4 ratio and tumor necrosis factor-alpha production. At the single cell level no TH 1/TH2 shifts were found. Remarkably, up-regulation of TH1 cytokines was accompanied by down-regulation of CCR1, CXCR3, and CCR5 expression. Neither CD4+ lymphocyte numbers nor IgG, IgM, and antithyroperoxidase levels, although higher in women then in men, were affected by cross-sex hormonal treatment. These results demonstrate that the capacity to develop a TH1 phenotype of peripheral blood lymphocytes is stimulated by androgens and is slightly inhibited by estrogens. These changes may be direct or indirect through the effects on other hormones.

Effect of 50- and 100-mg vitamin E supplements on cellular immune function in noninstitutionalized elderly persons.

BACKGROUND: It has been suggested that vitamin E can counteract the age-associated decline in cellular immune responsiveness (CIR). Particularly, T helper cell type 1 (Th1) activity, ie, interferon (IFN) gamma-producing Th1 activity and, hence, delayed-type hypersensitivity (DTH) would be enhanced by vitamin E supplementation. OBJECTIVE: Our aim was to study the effects of 6 mo supplementation with 50 and 100 mg vitamin E on CIR in the elderly. DESIGN: A double-blind, placebo-controlled trial was conducted in 161 healthy elderly subjects aged 65-80 y. CIR was measured in vivo by means of DTH skin tests and in vitro by assessing the production of interleukin (IL) 2, IFN-gamma (a typical Th1 cytokine), and IL-4 (a typical Th2 cytokine) by peripheral blood mononuclear cells after stimulation with phytohemagglutinin. RESULTS: Both DTH and IL-2 production showed a trend toward increased responsiveness with increasing dose of vitamin E. However, IFN-gamma production decreased whereas IL-4 production increased in the groups receiving vitamin E. Only the change in the number of positive DTH reactions was borderline significantly larger in the 100-mg vitamin E group than in the placebo group (P = 0.06, Bonferroni adjusted). Subjects receiving 100 mg vitamin E with low baseline DTH reactivity or who were physically less active had a significantly larger increase in the cumulative diameter of the skin induration resulting from the DTH test than did the placebo group (P = 0.03), although this difference was not significant after Bonferroni correction (P = 0.07). CONCLUSION: Possible beneficial effects of 100-mg vitamin E supplementation may be more pronounced in particular subgroups of elderly subjects.

Increased production of tumor necrosis factor alpha, and not of interferon gamma, preceding disease activity in patients with multiple sclerosis.

OBJECTIVE: To study whether tumor necrosis factor (TNF) alpha or interferon (IFN) gamma production by stimulated white blood cells precedes or accompanies clinical and magnetic resonance imaging signs of disease activity in patients with multiple sclerosis. DESIGN: Prospective study with a follow-up of 9 months. SETTING: Patients visiting an outpatient university clinic. PATIENTS: The 30 Amsterdam-based patients (28 completing all evaluations) participating in a multicenter, randomized, placebo-controlled, double-blind trial of a chimeric anti-CD4 antibody in the treatment of active relapsing-remitting and secondary progressive multiple sclerosis. Patients in both treatment arms were included, because for these patients anti-CD4 treatment in this study did not affect TNF-alpha and IFN-gamma production and did not reduce signs of disease activity on magnetic resonance imaging. MAIN OUTCOME MEASURE: Distribution of classes of TNF-alpha and IFN-gamma production (expressed as z scores) in patients with or without clinical or magnetic resonance imaging signs of disease activity. RESULTS: One month preceding exacerbations of multiple sclerosis, there was a shift toward higher z scores of TNF-alpha production (P<.05), but not of IFN-gamma production. There was no statistically significant relationship between IFN-gamma and TNF-alpha production and magnetic resonance imaging markers of multiple sclerosis activity. CONCLUSION: The production of TNF-alpha, and not of IFN-gamma, is significantly higher in patients with multiple sclerosis before exacerbations than in patients with stable disease. Although present, this relationship is too weak to use TNF-alpha production as a surrogate marker of disease activity in multiple sclerosis.

Increased MRI activity and immune activation in two multiple sclerosis patients treated with the monoclonal anti-tumor necrosis factor antibody cA2.

There is evidence that treatment with an antibody to tumor necrosis factor alpha (TNF alpha) improves an animal model of multiple sclerosis (MS) and is beneficial in two systemic inflammatory disease in humans, but there are no reports about anti-TNF treatment of MS. Therefore, we treated two rapidly progressive MS patients with intravenous infusions of a humanized mouse monoclonal anti-TNF antibody (cA2) in an open-label phase I safety trial and monitored their clinical status, gadolinium-enhanced brain magnetic resonance imaging (MRI), and peripheral blood and cerebrospinal fluid (CSF) immunologic status. We did not notice any clinically significant neurologic changes in either patient. The number of gadolinium-enhancing lesions increased transiently after each treatment in both patients. CSF leukocyte counts and IgG index increased after each treatment. The transient increase in the number of gadolinium-enhancing lesions that followed each infusion of cA2 together with the increase in cells and immunoglobulin in the CSF of each patient suggest that the treatment caused immune activation and an increase in disease activity. These results suggest that further use of cA2 in MS is not warranted and that studies of other agents that antagonize TNF alpha should be carried out with frequent monitoring of gadolinium-enhanced MRIs.

The development of anti-interleukin-2 (IL-2) antibodies in cancer patients treated with recombinant IL-2.

Serum samples from 217 cancer patients participating in phase I/II clinical trials were analysed for the development of anti-interleukin-2 (IL-2) antibodies. Patients received recombinant human IL-2 (rIL-2) by continuous intravenous infusion (c.i.v.; n = 86) or by subcutaneous (s.c.) injections (n = 131). Both patient groups developed anti-rIL-2 antibodies as detected by ELISA with similar frequencies and titres: 52% (median titre, 23) and 47% (median titre, 24), respectively. Using an IL-2-dependent T-cell proliferation assay, sera from 5 c.i.v.-treated patients (6%) and 13 s.c.-treated patients (10%) exhibited neutralising activity. Immunoabsorption studies with rIL-2-coated beads, demonstrated that in 8 of 15 patients with neutralising sera, the neutralising activity was correlated with specific anti-rIL-2 immunoglobulin. All 8 patients had received at least two cycles of rIL-2 by s.c. injections. Specific IL-2 neutralising activity affected both recombinant and natural IL-2 in all 8 patients. Development of anti-rIL-2 antibodies, irrespective of whether these exhibited neutralising activity or not, did not affect the frequency or duration of clinical responses.

A pilot study investigating the effects of orally administered pentoxifylline on selected immune variables in patients with multiple sclerosis.

Multiple sclerosis is probably mainly mediated by T-helper 1 (TH1)-lymphocytes. TH1-function can be down-regulated in vitro and in animal experiments by pentoxifylline. Therefore, we included 20 multiple sclerosis patients in an open label pilot trial of pentoxifylline. Outcome parameter was the effect of treatment on levels of various cytokines and adhesion molecules in cerebrospinal fluid and serum, on production of TH1- and TH2-cytokines using cell stimulation assays, as well as on measures of T-cell activation and proliferation. Kurtzke's EDSS was a secondary efficacy parameter. A convincing and consistent effect of pentoxifylline could not be demonstrated.

Synergistic effect of KRN7000 with interleukin-15, -7, and -2 on the expansion of human V alpha 24+V beta 11+ T cells in vitro.

KRN7000, (2S, 3S, 4R)-1-O-(alpha-D-galactopyranosyl)-2-(N-hexacosanoylamino)-1, 3, 4-octadecanetriol, has been shown to prevent tumor metastasis to the liver through the activation of natural killer (NK) T cells in mice. In this study, the proliferation of human NK T cells, which express an invariant T cell antigen receptor (TCR) consisting of a Valpha24 chain and a Vbeta11 chain, was investigated using KRN7000, interleukin (IL)-15, IL-7, and IL-2 in vitro. KRN7000 stimulated the expansion of Valpha24(+)Vbeta11(+) T cells derived from peripheral blood mononuclear cells in a dose-dependent fashion, with some fluctuation between donors. IL-15, IL-7, and IL-2 synergistically stimulated the expansion of Valpha24(+)Vbeta11(+) T cells when combined with KRN7000. Intracellular expression of interferon (IFN)-gamma and IL-4 in Valpha24(+)Vbeta11(+) T cells expanded in the presence of KRN7000 was identified using flow cytometry. Valpha24(+)Vbeta11(+) T cells, expanded in the presence of KRN7000, contained granzyme (Gr) B-positive granules and perforin-positive granules. The addition of IL-15 to the culture containing KRN7000 increased GrB expression in Valpha24(+)Vbeta11(+) T cells while IL-7 and IL-2 failed to do it. In conclusion, the antitumor effect of KRN7000 may depend, in part, on granule-mediated cell killing through the activation of NK T cells and IL-15 may potentiate this effect.