Pembrolizumab versus methotrexate, docetaxel, or cetuximab in recurrent or metastatic head and neck squamous cell carcinoma (KEYNOTE-040): Subgroup analysis by pattern of disease recurrence

BACKGROUND

In the phase 3 KEYNOTE-040 study, pembrolizumab prolonged OS versus chemotherapy in previously treated recurrent or metastatic (R/M) HNSCC. We present a post hoc subgroup analysis by disease recurrence pattern: recurrent-only, recurrent and metastatic (recurrent-metastatic), and metastatic-only HNSCC.

MATERIALS AND METHODS

Patients had HNSCC that progressed during or after platinum-containing treatment for R/M disease or had recurrence or progression within 3-6 months of previous platinum-containing definitive therapy for locally advanced disease. Patients were randomly assigned (1:1) to pembrolizumab 200 mg Q3W or investigator's choice of standards of care (SOC): methotrexate, docetaxel, or cetuximab. Outcomes included OS, PFS, ORR, and DOR. The data cutoff was May 15, 2017.

RESULTS

There were 125 patients (pembrolizumab, 53; SOC, 72) in the recurrent-only subgroup, 204 in the recurrent-metastatic subgroup (pembrolizumab, 108; SOC, 96), and 166 in the metastatic-only subgroup (pembrolizumab, 86; SOC, 80). The hazard ratio (95% CI) for death for pembrolizumab versus SOC was 0.83 (0.55-1.25) in the recurrent-only, 0.78 (0.58-1.06) in the recurrent-metastatic, and 0.74 (0.52-1.05) in the metastatic-only subgroups. PFS was similar between treatment arms in all subgroups. ORR was 22.6% for pembrolizumab versus 16.7% for SOC in the recurrent-only, 10.2% versus 6.3% in the recurrent-metastatic, and 15.1% versus 8.8% in the metastatic-only subgroups. DOR was numerically longer with pembrolizumab in all subgroups.

CONCLUSION

Pembrolizumab provided numerically longer OS and durable responses in all subgroups compared with SOC, suggesting that patients with previously treated R/M HNSCC benefit from pembrolizumab regardless of recurrence pattern.

Transcriptomic signature related to poor welfare of sport horses

The improvement of horse welfare through housing conditions has become a real issue in recent years and have highlighted the detrimental effect of individual housing of horses on their health and behaviour. In this new study, we analysed the blood transcriptome of 45 sport horses housed individually that were previously examined for their behaviour and gut microbiota. We performed differential and regression analyses of gene expression, followed by downstream bioinformatic analyses, to unveil the molecular pathways related to the behavioural changes associated with welfare impairment in these sport horses. We found that aggressiveness towards humans was the behavioural indicator the most correlated to blood gene expression and that the pathways involved belonged mainly to systemic inflammation. In contrast, the correlations between genes, alert postures and unresponsiveness towards the environment were weak. When blood gene expression profiling was combined with faecal microbiota of a sub-population of horses, stereotypies came out as the most correlated to blood gene expression. This study shows that aggressiveness towards humans and stereotypies are behavioural indicators that covary with physiological alterations. Further studies are needed regarding the biological correlates of unresponsiveness to the environment and alert postures.

Horse welfare: A joint assessment of four categories of behavioural indicators using the AWIN protocol, scan sampling and surveys

Domesticated horses ( Equus caballus) can be exposed to a compromised welfare state and detecting a deterioration in welfare is essential to modify the animals' living conditions appropriately. This study focused on four categories of behavioural indicators, as markers of poor welfare: stereotypies, aggressiveness towards humans, unresponsiveness to the environment and hypervigilance. In the scientific literature, at least three assessment methods can be used to evaluate them: the Animal Welfare Indicators (AWIN) protocol, behavioural observations using scans and surveys. The question remains as to whether all these three methods allow an effective assessment of the four categories of behavioural indicators. To address this issue, the repeatability at a three-month interval and convergent validity of each measure (correlations between methods) were investigated on 202 horses housed in loose boxes. Overall, the repeatability and convergent validity were limited, highlighting the difficulty in assessing these indicators in horses. However, stereotypies and aggressiveness measures showed higher repeatability and convergent validity than those of unresponsiveness to the environment and hypervigilance. Behavioural observations using scans enabled the four categories of behavioural indicators to be detected more effectively. Suggestions of improvements are proposed for one-off measures such as those performed with the AWIN protocol. Regardless of the assessment method, very limited correlations were observed between the four categories of behavioural indicators, suggesting that they should all be included in a set of indicators used to assess the welfare state of horses, in conjunction with physiological and health measures.

Serum acylcarnitine profile in endurance horses with and without metabolic dysfunction

Mitochondrial β-oxidation is essential in fat metabolism and can be monitored with blood acylcarnitine profiling, as partly degraded fatty acids accumulate as their carnitine esters. To guarantee continuous energy supply during long-distance exercise, endurance horses oxidise considerable amounts of fat in the mitochondrion. In endurance races over 80 km, glycogen depletion is evident in equine slow-twitch high oxidative muscle fibres and as a consequence, horses participating in endurance races over 80 km rely almost entirely on β-oxidation of fatty acids. This study investigated mitochondrial fatty acid β-oxidation in endurance horses exposed to long-distance exercise. Electrospray tandem mass spectrometry analysis of serum acylcarnitine profiles from 10 Arab horses was performed before and after a 160 km endurance race. Results were analysed statistically using ANOVA. Mean speed over the entire race in finishing horses was 16.7 ± 1.2 km/h. Endurance exercise increased mitochondrial β-oxidation approximately eight-fold (pre-race, 5648.62 ± 1508.52 nmol/L; post-race, 44,243.17 ± 11,504.45 nmol/L; P = 0.001). In these horses, there was an approximately 17-fold increased lipolysis, as demonstrated by elevated serum concentrations of non-esterified fatty acids (NEFA; pre-race, 0.08 ± 0.08 mmol/L; post-race, 1.32 ± 0.36 mmol/L; P < 0.001). In comparison, four Arab horses with poor performance showed an approximately five-fold increase in mitochondrial β-oxidation (pre-race, 5286.17 ± 3355.16 nmol/L; post-race, 26,660.57 ± 10,064.27 nmol/L; P = 0.009); there was a 29-fold increase in NEFA (pre-race, 0.02 ± 0.01 mmol/L; post-race, 0.58 ± 0.07 mmol/L; P = 0.006) in these horses. Similar post-exercise free carnitine:acetylcarnitine ratios in both groups suggest that the availability of carnitine in long-distance endurance horses might limit performance.

[Head and neck cancer treatment in the elderly]

We compared the treatment modalities as well as the oncologic outcome between young elderly (65-79 years old), elderly (>80 years old) and the reference population (<65 years old.) We reviewed 1047 patients treated between 2002 and 2012. Tumor sites, TNM stages, type of treatment, and the oncologic results are compared with survival statistics. The elderly group was associated with an increase in palliative treatment, more women and advanced T stages. For the 947 patients treated with curative intent, 5 year recurrence free survival was comparable. The overall-survival decreases with the age because of intercurrent deaths. Nevertheless, the treatment efficacy is similar. In conclusion, an advanced age is associated with worse survival, without a decrease in loco-regional control. The chronological age should not be used as a predictive factor for treatment response.

[The Onco-hematology clinical research unit at the Geneva University Hospital: example of a fruitful public-private partners]

A better understanding of the molecular deregulation leading to carcinogenesis allows the development of numerous novel targeted therapeutic candidates. Clinical research in oncology is a critical step to evaluate in a thorough manner the safety and efficacy of these innovative compounds. During the last four years the fruitful partnership between the Geneva University Hospitals and the Dr. Henri Dubois-Ferriere Dinu Lipatti Foundation lead to a dedicated clinical research unit for cancer patients with a staff of ten people. Since 2010, more than 300 patients were enrolled in more than 70 distinct clinical trials evaluating novel therapies for both solid tumors and hematologic malignancies. Interestingly, classical cytostatic drugs now represent only a small fraction of the new anti-cancer therapies in the pipeline.

[The role of surgery in early stage small cell lung cancer: should it be re-evaluated?]

Two historical randomized controlled trials have demonstrated that chemo-radiotherapy offers the best survival advantage over surgery in small cell lung carcinoma (SCLC) and led to abandon surgery for the treatment of SCLC. Yet, widespread use of CT scanning increases the detection of early and very early stage SCLC. Therefore, the traditional 2 stages classification scheme--namely limited and extensive stage disease--is no longer sufficient for such early stage disease and must be completed by the TNM classification. Although randomized controlled trials are lacking, retrospective case series and large population databases suggest a beneficial role of surgery for the earliest SCLC stages. It is thus currently recommended to consider surgery in the multimodal treatment of stage I SCLC.

Analysis of raw hams using SELDI-TOF-MS to predict the final quality of dry-cured hams

The relationship between protein profiles of Gluteus medius (GM) muscles of raw hams obtained from 4 pure breed pigs (Duroc, Large White, Landrace, and Piétrain) with the final quality of the Semimembranosus and Biceps femoris muscles of dry-cured hams was investigated. As expected, Duroc hams showed higher levels of marbling and intramuscular fat content than the other breeds. Piétrain hams were the leanest and most conformed, and presented the lowest salt content in dry-cured hams. Even if differences in the quality traits (colour, water activity, texture, composition, intramuscular fat, and marbling) of dry-cured hams were observed among the studied breeds, only small differences in the sensory attributes were detected. Surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS) was used to obtain the soluble protein profiles of GM muscles. Some associations between protein peaks obtained with SELDI-TOF-MS and quality traits, mainly colour (b*) and texture (F(0), Y(2), Y(90)) were observed. Candidate protein markers for the quality of processed dry-cured hams were identified.

[Anticancer drugs under pressure]

Angiogenesis inhibitor drugs, targeting VEGF (vascular endothelial growth factor) are used increasingly in oncology for a wide range of advanced cancers (colorectal cancer, lung cancer, renal cell cancer,...). Generally, they are well tolerated but cardiovascular and renal side effects may appear. The most frequent complications are hypertension and proteinuria which, very often, remain asymptomatic. Therefore, they have to be searched for systematically before and during the treatment. Sometimes, anti-hypertensive medication is needed. We are just beginning to understand the pathophysiological mechanisms of antiangiogenic therapies. Only a multidisciplinary approach will improve our knowledge of those target agents and allow a better management of the cancer patient.

[Targeted therapy in lung cancer: molecular testing using cytological specimens]

Important advances in lung cancer treatment have been made over the last decade. Several drugs designed to target molecular pathways involved in cancer-cell growth and survival have been shown to be effective in a selected fraction (<20%) of non-small cell lung cancer patients. Somatic mutations in several genes (i.e.: EGFR and KRAS) can predict patient's response to targeted therapies. Those mutations are commonly detected on histopathological samples (core-needle biopsy/ surgical resection). However, when tissue biopsies are not available, molecular testing has to be performed on cytological specimens. Issues raised by molecular testing on cytological specimen are discussed in this article.

Cell encapsulation technology as a novel strategy for human anti-tumor immunotherapy

Granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant in autologous cell-based anti-tumor immunotherapy has recently been approved for clinical application. To avoid the need for individualized processing of autologous cells, we developed a novel strategy based on the encapsulation of GM-CSF-secreting human allogeneic cells. GM-CSF-producing K562 cells showed high, stable and reproducible cytokine secretion when enclosed into macrocapsules. For clinical development, the cryopreservation of these devices is critical. Thawing of capsules frozen at different time points displayed differences in GM-CSF release shortly after thawing. However, similar secretion values to those of non-frozen control capsules were obtained 8 days after thawing at a rate of >1000 ng GM-CSF per capsule every 24 h. For future human application, longer and reinforced capsules were designed. After irradiation and cryopreservation, these capsules produced >300 ng GM-CSF per capsule every 24 h 1 week after thawing. The in vivo implantation of encapsulated K562 cells was evaluated in mice and showed preserved cell survival. Finally, as a proof of principle of biological activity, capsules containing B16-GM-CSF allogeneic cells implanted in mice induced a prompt inflammatory reaction. The ability to reliably achieve high adjuvant release using a standardized procedure may lead to a new clinical application of GM-CSF in cell-based cancer immunization.

Comparative proteomic profiling of 2 muscles from 5 different pure pig breeds using surface-enhanced laser desorption/ionization time-of-flight proteomics technology

The objectives of this study were to evaluate the influence of different pure pig breeds and muscle types on the expression of muscle proteins, as well as their interactions, and second, to find biomarkers for breed and muscle types. A total of 126 male pigs, including 43 Landrace, 21 Duroc, 43 Large White, 13 Pietrain, and 6 Belgian Landrace, were slaughtered at the age of 174 +/- 6 d. Samples from the semimembranosus muscle (SM) and LM were collected 24 h postmortem. Proteomic spectra were generated on an anion exchanger (Q10), a cation exchanger (CM10), and on immobilized metal affinity capture (IMAC30) ProteinChip arrays and analyzed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry ProteinChip techniques. Breed and muscle type did not affect the number of peaks per spectrum but, interestingly, affected the average intensity of the peaks. Of these peaks, a total of 4 proved to be potential protein biomarkers to differentiate LM or SM muscles, and 2 to classify specific breed types. Additionally, several peaks influenced by the interaction between muscle and breed types could correctly classify pig muscles according to their breed. Further studies need to be carried out to validate and identify these potential protein biomarkers for breed and muscle types in finishing pigs.

Burdizzo pre-pubertal castration effects on performance, behaviour, carcass characteristics, and meat quality of Holstein bulls fed high-concentrate diets

The effects of Burdizzo pre-pubertal castration on performance, behaviour, carcass, and meat quality of Holstein bulls fed high-concentrate diets were evaluated. Two hundred bulls (8.0±0.42 months old) were randomly assigned to control (CTR) or Burdizzo castration (BURD). After 121d, ADG, BW, and HCW were greater in CTR animals than in BURD animals, as well as, the agonistic and sexual behaviour. However, carcass fatness and intramuscular LT (longissimus thoracis) fat percentage were greater in BURD animals than in CTR animals. Additionally, CTR animals showed lower L(∗), a(∗), and b(∗) than BURD. The WBSF was smaller (P<0.01) in BURD than in CTR bulls at all ageing days, and in both treatments decreased (P<0.01) from 0 to 7d of ageing. Additionally, at day 0 of ageing, meat from BURD animals showed similar WBSF to meat from CTR bulls after 7d of ageing. However, 23% of BURD animals did not have a complete testicular atrophy, suggesting that the method of castration was not completely effective.

Multicenter phase II trial of gefitinib first-line therapy followed by chemotherapy in advanced non-small-cell lung cancer (NSCLC): SAKK protocol 19/03

BACKGROUND

Gefitinib is active in patients with pretreated non-small-cell lung cancer (NSCLC). We evaluated the activity and toxicity of gefitinib first-line treatment in advanced NSCLC followed by chemotherapy at disease progression.

PATIENTS AND METHODS

In all, 63 patients with chemotherapy-naive stage IIIB/IV NSCLC received gefitinib 250 mg/day. At disease progression, gefitinib was replaced by cisplatin 80 mg/m(2) on day 1 and gemcitabine 1250 mg/m(2) on days 1, 8 for up to six 3-week cycles. Primary end point was the disease stabilization rate (DSR) after 12 weeks of gefitinib.

RESULTS

After 12 weeks of gefitinib, the DSR was 24% and the response rate (RR) was 8%. Median time to progression (TtP) was 2.5 months and median overall survival (OS) 11.5 months. Never smokers (n = 9) had a DSR of 56% and a median OS of 20.2 months; patients with epidermal growth factor receptor (EGFR) mutation (n = 4) had a DSR of 75% and the median OS was not reached after the follow-up of 21.6 months. In all, 41 patients received chemotherapy with an overall RR of 34%, DSR of 71% and median TtP of 6.7 months.

CONCLUSIONS

First-line gefitinib monotherapy led to a DSR of 24% at 12 weeks in an unselected patients population. Never smokers and patients with EGFR mutations tend to have a better outcome; hence, further trials in selected patients are warranted.

Association between animal, transportation, slaughterhouse practices, and meat pH in beef

The objective of this study was to evaluate the influence of factors related to animal, farm, transportation, and animal handling at the slaughterhouse, as well as their interactions, on pH of beef meat. A total of 5494 cattle (343±45d of age) from 181 different Spanish farms were surveyed during three seasons (spring, summer, and winter) and a total of 25 pre-slaughter variables were recorded. Meat pH was measured at the Longissimus dorsi 24h post-mortem (pH(24)). After a variable selection procedure, a mixed-effects logistic regression model was conducted with 5 variables (1 random and 4 fixed) to identify the main factors, and their interactions, affecting meat pH(24). Average incidences of meat pH(24) greater than 5.8 and 6.0 were 13.89% and 4.02%, respectively. The variability of meat pH(24) explained with studied factors and their interactions was only 4.9%, a value too low to allow making technical decisions to improve meat pH(24) in the Spanish market considering the variables studied.

Increasing the amount of n-3 fatty acid in meat from young Holstein bulls through nutrition1

Fifty-four Holstein bulls were blocked by initial BW (301 +/- 7.4 kg) and randomly assigned to 6 treatments following a 3 x 2 factorial arrangement, with 3 concentrate lipid levels (5, 8, and 11% of DM) and 2 lipid sources (whole canola seed and whole linseed), with the objective of evaluating the possibility of increasing the content of n-3 fatty acids in meat. Concentrates (mostly corn meal) were isonitrogenous and isocaloric. Concentrate and straw were both fed ad libitum. Animal BW was recorded every 2 wk, and feed consumption was recorded weekly. Ruminal pH and VFA concentrations were determined monthly. Bulls were transported to the slaughterhouse when they achieved the target slaughter weight of 443 kg (after 105 +/- 4 d of fattening). After slaughter, a sample of LM from the sixth to the eighth ribs was dissected and analyzed for intramuscular fat content and fatty acid profile. Dietary lipid source did not affect overall animal performance, rumen fermentation, or carcass quality. Rumen pH was >6.0 despite consumption by the bulls of large amounts of concentrate. In bulls fed linseed, the percentage of n-3 fatty acids in LM increased linearly with lipid level, whereas in bulls fed canola seed it remained constant. The ratio of n-6:n-3 fatty acids was lower (P < 0.01) in the LM of bulls fed linseed (10.0) than in those fed canola seed (26.0). The content of cis-9, trans-11-CLA in the LM tended (P = 0.06) to be greater in the bulls fed linseed than in those fed canola seed (62.9 vs. 49.2 mg/kg of LM, respectively). Concentration of n-3 fatty acids in meat of bulls fed high-concentrate diets can be enhanced by whole linseed supplementation without affecting animal performance, ruminal fermentation, or carcass quality.

[Screening for lung cancer in 2006: is there a validated test?]

Lung cancer is by far the most common cause of death from any tumor. This is partly due to the late stage of most bronchial carcinoma at the time of diagnosis. Curative treatment by surgery is possible only for localized disease. Hope to decrease mortality by screening techniques such as radiography and/or sputum cytology led to several large trials in the eighties. None of these studies were able to show a meaningful decrease in mortality. Improvement in medical imaging lead to a new hope that low-dose CT scan may be an efficient screening tool for lung cancer. This article reviews the data currently available. So far no screening technique has been able to demonstrate an impact on lung cancer mortality despite the higher sensitivity to detect smaller lung tumors. Therefore, in 2006, screening for lung cancer can not be recommended.

Guarantying the quality of chemotherapy: from the order to the administration

Ensuring the quality and security when prescribing drugs like chemotherapies is a complex task if one wants to cover the whole chain from the prescribing physician to the administrant nurse. At the University hospitals of Geneva, new applications covering the whole chain from the prescription up to and including the fabrication of the products have been developed in three phases and are being used in a production stage. In order to cover the "last yard" at the bed level, a fourth phase has been started with a pilot study based on labels containing RFID chips for preparations and for patients. The last phase will make use of all traceability data acquired from the prescription to the preparation to validate that the right product is administered to the right patient, and to record who is administrating it.

Overlapping roles for granulocyte-macrophage colony-stimulating factor and interleukin-3 in eosinophil homeostasis and contact hypersensitivity

Studies of mice rendered deficient in granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) have established unique roles for these cytokines in pulmonary homeostasis, resistance to infection, and antigen-specific T- and B-cell responses. In addition to these distinctive properties, however, GM-CSF and IL-3 also stimulate the development and activation of hematopoietic cells in many similar ways, raising the possibility that each factor might partially compensate for the other's absence in singly deficient mice. To test whether endogenous GM-CSF and IL-3 mediate redundant functions in vivo, we generated mice lacking both cytokines through sequential gene targeting experiments in embryonic stem (ES) cells. Surprisingly, doubly deficient animals, but not single knockouts, showed increased numbers of circulating eosinophils. Doubly deficient mice, moreover, developed weaker contact hypersensitivity reactions to haptens applied epicutaneously than mice deficient in either factor alone. Together, these findings delineate overlapping roles for GM-CSF and IL-3 in hematopoiesis and immunity. (Blood. 2001;97:922-928)

Tumor cell vaccine elicits potent antitumor immunity after allogeneic T-cell-depleted bone marrow transplantation

Allogeneic bone marrow transplantation (BMT) is currently restricted to hematological malignancies because of a lack of antitumor activity against solid cancers. We have tested a novel treatment strategy to stimulate specific antitumor activity against a solid tumor after BMT by vaccination with irradiated tumor cells engineered to secrete granulocyte-macrophage colony-stimulating factor (GM-CSF). Using the B16 melanoma model, we found that vaccination elicited potent antitumor activity in recipients of syngeneic BMT in a time-dependent fashion, and that immune reconstitution was critical for the development of antitumor activity. Vaccination did not stimulate antitumor immunity after allogeneic BMT because of the post-BMT immunodeficiency associated with graft-versus-host disease (GVHD). Remarkably, vaccination was effective in stimulating potent and long-lasting antitumor activity in recipients of T-cell-depleted (TCD) allogeneic bone marrow. Recipients of TCD bone marrow who showed significant immune reconstitution by 6 weeks after BMT developed B16-specific T-cell-cytotoxic, proliferative, and cytokine responses as a function of vaccination. T cells derived from donor stem cells were, therefore, able to recognize tumor antigens, although they remained tolerant to host histocompatibility antigens. These results demonstrate that GM-CSF-based tumor cell vaccines after allogeneic TCD BMT can stimulate potent antitumor effects without the induction of GVHD, and this strategy has important implications for the treatment of patients with solid malignancies.

Cytokine-secreting tumor cell vaccines

Modification of the tumor microenvironment with gene transfer techniques stimulates two immune mechanisms that effectuate tumor destruction. One involves improved tumor-antigen presentation for the development of specific cellular and humoral immunity. The second involves compromise of the tumor vasculature by soluble factors and leukocytes.

Differences in dendritic cells stimulated in vivo by tumors engineered to secrete granulocyte-macrophage colony-stimulating factor or Flt3-ligand

Both granulocyte-macrophage colony-stimulating factor (GM-CSF) and flt3-ligand (FL) induce the development of dendritic cells (DCs). To compare the functional properties of DCs stimulated by these cytokines in vivo, we used retroviral-mediated gene transfer to generate murine tumor cells secreting high levels of each molecule. Injection of tumor cells expressing either GM-CSF or FL resulted in the dramatic increase of CD11c+ cells in the spleen and tumor infiltrate. However, vaccination with irradiated, GM-CSF-secreting tumor cells stimulated more potent antitumor immunity than vaccination with irradiated, FL-secreting tumor cells. The superior antitumor immunity elicited by GM-CSF involved a broad T cell cytokine response, in contrast to the limited Thl response elicited by FL. DCs generated by GM-CSF were CD8alpha- and expressed higher levels of B7-1 and CD1d than DCs cells generated by FL. Injection sites of metastatic melanoma patients vaccinated with irradiated, autologous tumor cells engineered to secrete GM-CSF demonstrated similar, dense infiltrates of DCs expressing high levels of B7-1. These findings reveal critical differences in the abilities of GM-CSF and FL to enhance the function of DCs in vivo and have important implications for the crafting of tumor vaccines.

Role for interleukin-3 in mast-cell and basophil development and in immunity to parasites

The cytokine interleukin-3 (IL-3), which can be derived from T cells and other sources, is a potentially important link between the immune and haematopoietic systems. IL-3 may be particularly critical for the development, survival and function of tissue mast cells and blood basophils, which are thought to be important effector cells in immunity to parasites and other immunological responses, such as allergic reactions. Here we show, using IL-3-deficient mice, that IL-3 is not essential for the generation of mast cells or basophils under physiological conditions, but that it does contribute to increased numbers of tissue mast cells, enhanced basophil production, and immunity in mice infected with the nematode Stronglyoides venezuelensis. Parasite expulsion and mast-cell development are impaired even more severely in IL-3-deficient mice that also show a marked reduction in signalling by c-kit. These findings establish a role for IL-3 in immunity to parasites and indicate that one of the functions of IL-3 in host defence against infection is to expand populations of haematopoietic effector cells.

Involvement of interleukin-3 in delayed-type hypersensitivity

The in vivo functions of interleukin-3 (IL-3) were investigated by generating IL-3-deficient mice. Although hematopoiesis was unimpaired in homozygous mutant animals, contact hypersensitivity reactions were compromised. IL-3 was required for efficient priming of hapten-specific contact hypersensitivity responses, but was dispensable for T-cell-dependent sensitization to tumor cells. These findings reveal a critical role for IL-3 in some forms of delayed-type hypersensitivity.