EGFR-mutated advanced lung cancer. Data from a single institution, the Hospital of Leon, in Spain.

INTRODUCTION: 10-16% of non-small cell lung cancer (NSCLC) cases have the epidermal growth factor receptor (EGFR) amplified and/or mutated. Studies show that EGFR tyrosine kinase inhibitors (TKIs) significantly prolong progression-free survival (PFS) in patients with advanced NSCLC compared to those treated with platinum-based chemotherapy (CT) doublets. Our aim is to perform a real-world survival analysis of patients treated with TKI as first-line therapy at the Hospital of Leon (CAULE) in Spain. The impact on global survival rates and responses to clinical and histopathological factors were also analyzed. MATERIAL AND METHODS: We retrospectively reviewed patients diagnosed with EGFR-mutated NSCLC who received treatment with EGFR-TKI in the Department of Oncology at the University of Leon Health Center complex between March 2011 and June 2018. Data was analyzed with Kaplan-Meier and Cox regression models to show overall survival (OS), progression-free survival (PFS), and the associated variables. RESULTS: 53 patients were included in the study, 50% (n = 27) were treated with gefitinib, 32% (n = 18) with erlotinib and 10% (n = 6) with afatinib. The median OS and PFS were 27.7 months (95% CI: 21-33.8 months) and 18 months (95% CI 14.25-21.89 months), respectively. The variables associated with OS and with PFS were exon19 deletion as a protective factor and presence of extrathoracic metastasis as a risk factor. The most frequent adverse effects were rash, diarrhea, asthenia, and conjunctivitis. CONCLUSIONS: Real-world analysis of this data confirms that treatment with TKI is beneficial for patients diagnosed with EGFR-mutated NSCLC. Our OS outcomes were similar to those reported in clinical trials.

Mycobacterium abscessus Infected Neutrophils as an In Vitro Model for Bronchiectasis. Neutrophils Prevent Mycobacterial Aggregation

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Increased serum concentrations of estrogen-induced growth factors Midkine and FGF2 in NF1 patients with plexiform neurofibroma.

Neurofibromatosis type 1 (NF1) predisposes to the development of dermal and plexiform neurofibromas and serum of NF1 patients stimulates neurofibroma proliferation in vitro. This study aimed to determine whether, in NF1 patients, serum levels of midkine (MK) and fibroblast growth factor 2 (FGF2) were associated with the number and/or type of neurofibromas. In addition, their concentrations were correlated with serum levels of dehydroepiandrosterone sulfate (DHEAS), a neurosteroid secreted by the peripheral nervous system. We performed a case control-study and measured, by ELISA assay, serum concentrations of MK, FGF2, and DHEAS in 20 NF1 patients and 30 controls. We found increased serum levels of MK and FGF2 in NF1 patients between 30 and 50 years old. Their concentrations were significantly higher in NF1 patients with plexiform neurofibromas than in controls (P=0.003 for MK and P=0.008 for FGF2). As an underlying hormonal regulation was suspected, DHEAS serum levels were measured but no difference was observed between patients and controls. We also observed a strong association between MK and FGF2 levels (P=0.0001) in NF1 patients and controls. In conclusion, we point out MK and FGF2 as biomarkers for plexiform neurofibroma in NF1 patients. As both growth factors are estrogen-responsive genes and neurofibromin is a co-repressor of estrogen receptor alpha activity, we suggest that the increased serum levels of MK and FGF2 observed in NF1 patients might be due to estradiol hypersensitivity.

Mycobacterium avium complex infected cells promote growth of the pathogen Pseudomonas aeruginosa.

Bronchiectasis is considered a consequence of the neutrophilic inflammatory response to infection. Mycobacterial infections, mainly from the Mycobacterium avium complex and M. abscessus, have been inextricably linked to bronchiectasis development. The most important pathogen that infect patients with bronchiectasis is Pseudomonas aeruginosa, associated with an increased risk of death. Patients with bronchiectasis are often co-infected with P. aeruginosa and M. avium complex, and it was studied whether they interacted in immune cell cultures. Peripheral blood mononuclear cells from healthy volunteers were infected overnight with clinical isolates of mycobacteria, 18 h later co-infected with P. aeruginosa and Pseudomonas multiplication was quantified. Inoculated P. aeruginosa multiply faster when cells were previously infected in vitro with M. avium complex or M. tuberculosis, but not with M. kansasii or M. gordonae, mycobacteria not regularly isolated from patients with bronchiectasis. The interaction between mycobacteria and P. aeruginosa also takes place in the absence of cells, but to a lower degree. Growth of Staphylococcus aureus, less frequently co-isolated with mycobacteria, was not affected by previous infection with mycobacteria. Surprisingly, multiplication of P. aeruginosa in neutrophil cultures did not vary in the presence of mycobacteria. Nevertheless, co-infection of mycobacteria and P. aeruginosa induced the production of IL-1ß, a mediator of neutrophilic inflammation. P. aeruginosa stimulation by mycobacteria provides evidence for explaining their common clinical association. Strategies to control mycobacteria may be useful to impair P. aeruginosa colonization.

A strategy based on Amplified Fragment Length Polymorphism (AFLP) for routine genotyping of nontuberculous mycobacteria at the clinical laboratory.

The increasing worldwide incidence of mycobacteriosis and the need to achieve improved clinical management makes nontuberculous mycobacteria (NTM) genotyping a useful tool. However, because of technical difficulties, medium size microbiology laboratories do not attempt to compare the genetic patterns that each of their isolates present. We have aimed to optimize a genotyping method with a reduced hands-on experimental time and that requires few technical resources. A strategy based on the Amplified Fragment Length Polymorphism (AFLP) methodology was developed using two rare-cutters enzymes (SacI and BglII). One out of seven primers was sequentially used in each amplification reaction that was analyzed by agarose gel electrophoresis. This approach makes it possible the timely genotyping of a moderate number of strains and its characterization without the need of image analysis software. We have genotyped 28 Mycobacterium intracellulare and 4 M. abscessus. Clinical researchers are encouraged to routinely genotype their NTM isolates.

In vitro infection with Mycobacterium tuberculosis induces a distinct immunological pattern in blood from healthy relatives of tuberculosis patients.

Part of the susceptibility to tuberculosis has a genetic basis, which is clear in primary immunodeficiencies, but is less evident in apparently immunocompetent subjects. Immune responses were analysed in blood samples from tuberculosis patients and their healthy first-degree relatives who were infected in vitro with mycobacteria (either Mycobacterium tuberculosis or M. bovis BCG). The antimicrobial activity against M. tuberculosis in blood from relatives was significantly lower than that observed in healthy controls. Tuberculosis patients exhibited a higher number of neutrophils, and monocyte phagocytosis was inhibited in both relatives and tuberculosis patients. A remarkable finding was that the production of reactive oxygen species by infected neutrophils was higher in relatives than in healthy controls. A higher production of TNFα in infected blood from relatives was also observed. These results may indicate that relatives display a stronger inflammatory response and that their immune response to M. tuberculosis is different from those of unrelated controls. First-degree relatives may represent a highly informative group for the analysis of tuberculosis susceptibility.

The role of EZH2 in overall survival of colorectal cancer: a meta-analysis.

Enhancer of zeste homolog 2 (EZH2) is the catalitic subunit of polycomb repressive complex 2 and mediates gene silencing. EZH2 is overexpressed in many cancers and correlates with poor prognosis. The role of the gene EZH2 in colorectal cancer survival is uncertainly, the aim of this study is clear this relationship. Relevant literaure was searched from electronic databases. A meta-analysis was performed with elegible studies which quantitatively evaluated the relationship between EZH2 overexpression and survival of patients with colorectal cancer. Survival data were aggregated and quantitatively analyzed. We performed a meta-analysis of 8 studies (n = 1059 patients) that evaluated the correlation between EZH2 overexpression and survival in patients with colorectal cancer. Combined hazard ratios suggested that EZH2 overexpression was associated with better prognosis of overall survival (OS) HR(hazard ratio) = 0.61 95% CI (0.38-0.84) We performed bias analysis according Egger and Begg,s test and we did not find publication bias. EZH2 overexpression indicates a better prognosis for colorectal cancer.

Immunological response to Mycobacterium tuberculosis infection in blood from type 2 diabetes patients.

The convergence of tuberculosis and diabetes represents a co-epidemic that threatens progress against tuberculosis. We have investigated type 2 diabetes as a risk factor for tuberculosis susceptibility, and have used as experimental model whole blood infected in vitro with Mycobacterium tuberculosis. Blood samples from diabetic patients were found to have a higher absolute neutrophil count that non-diabetic controls, but their immune functionality seemed impaired because they displayed a lower capacity to phagocytose M. tuberculosis, a finding that had been previously reported only for monocytes. In contrast, an increased production of TNFα was detected in infected blood from diabetic patients. Despite the altered phagocytic capacity showed by cells from these patients, the antimicrobial activity measured in both whole blood and monocyte derived macrophages was similar to that of controls. This unexpected result prompts further improvements in the whole blood model to analyze the immune response of diabetes patients to tuberculosis.

Plasma contributes to the antimicrobial activity of whole blood against Mycobacterium tuberculosis.

The whole blood model for infection has proven useful to analyze the immunological response to Mycobacterium tuberculosis, because it exerts a significant antimicrobial activity. Although this activity has been generally assumed to be cellular, we have found that the leukocyte fraction of blood from healthy volunteers did not kill the bacilli. We have discovered that plasma was responsible for a large proportion, but not all, of the antimicrobial activity. Furthermore, infected monocytes controlled the mycobacterial multiplication when cultivated in the presence of plasma. Intriguingly, serum from the same donors did not share this activity, although it was able to eliminate the non-pathogenic Mycobacterium gordonae To identify the remaining components that participate in the antimycobacterial activity we fractionated blood in leukocytes, plasma, erythrocytes and platelets, and analyzed the bactericidal power of each fraction and their combinations using a factorial design. We found that erythrocytes, but not platelets, participated and showed by flow cytometry that mycobacteria physically associated with erythrocytes. We propose that in exposed healthy individuals that show 'early clearance' of the mycobacteria, the innate response is predominantly humoral, probably through the effect of antimicrobial peptides and proteins.

Características clínicas, anatomopatológicas y moleculares en casos de cáncer colorrectal según localización tumoral y grado de diferenciación / Clinical, anatomopathological and molecular characteristics of colorectal cancer by tumor location and degree of differentiation

Objetivos: El cáncer colorrectal (CCR) presenta elevada incidencia y mortalidad con diferentes tendencias según localización anatómica y otras características anatomopatológicas que parecen vinculadas a cambios tanto a la exposición a factores de riesgo como al diagnóstico siendo esencial una adecuada filiación tumoral para valorar el efecto de dichos factores en la aparición, diagnóstico y progresión de la enfermedad. El objetivo fue describir las características clínicas y anatomopatológicas de pacientes diagnosticados de CCR en el Área de Salud de León en función de la localización tumoral y del grado de diferenciación. Métodos: Se estudió una serie de 408 casos de entre 25 y 85 años con diagnóstico confirmado de CCR, recogiéndose información de características clínicas y anatomopatológicas y de los biomarcadores analizados en la rutina clínica. Se realizó análisis univariable y bivariable según el grado de diferenciación y la localización tumoral. Resultados: El tamano tumoral disminuye desde colon proximal a recto (Colon Proximal = 5,13 cm: Colon Distal = 4,09cm: Recto = 3,17cm; p< 0,001) siendo el TNM también mayor en zonas proximales. Los adenocarcinomas mucinosos son más frecuentes en tumores pobremente diferenciados que en bien diferenciados (23,1% vs 5,5%). Las invasiones linfática, venosa y peritumoral son más frecuentes con menor grado de diferenciación. Conclusiones: La distribución del estadio tumoral en función de la localización tiene estadios TNM más avanzados en zonas proximales, lo que podría asociarse a una menor detección precoz en dichos casos. La asociación entre invasión venosa y linfática con el grado de diferenciación es poco conocida requiriéndose estudios que aclaren su posible interés pronóstico.

Aims: Colorectal cancer (CRC) has a high incidence and mortality, with different patterns depending on anatomical location and other pathological characteristics that appear linked to changes in exposure risk factors exposure as well as the diagnosis. All these make it essential to determine the source of the tumour to properly assess the effect of these factors in the development, diagnosis and progression of the disease. The aim was to describe the clinical and anatomical-pathological characteristics of patients diagnosed with CRC in the Health Area of Leon (ASL) based on their location and degree of tumour differentiation. Methods: Information was collected on the clinical and pathological characteristics, including biological markers analysed in clinical routine of 408 patients between 25 and 85 years with a confirmed diagnosis of CRC, and residents in ASL at least six months before diagnosis. Univariate and bivariate analyses were performed according to the degree of differentiation and tumour location. Results: Tumour size decreases from the colon to the rectum from location decline proximal colon to the rectum (Proximal Colon = 5.13cm; Distal Colon = 4.09cm; Rectum = 3.17cm, P< 0.001), with the TNM stage also being higher in proximal areas. Mucinous adenocarcinomas are more frequent in poorly differentiated than in well differentiated tumours (23.1% vs 5.5%). Lymphatic, venous and peri-tumour invasions are more common in poorly differentiated tumours. Conclusions: The distribution in accordance with the location has more advanced TNM stages in the proximal areas, which could be related to the poorer early diagnosis in proximal areas. The association between venous and lymphatic invasion with the degree of differentiation is poorly understood, and requires studies to clarify their possible prognostic interest.

Microarray analysis of Mycobacterium tuberculosis-infected monocytes reveals IL26 as a new candidate gene for tuberculosis susceptibility.

Differences in the activity of monocytes/macrophages, important target cells of Mycobacterium tuberculosis, might influence tuberculosis progression. With the purpose of identifying candidate genes for tuberculosis susceptibility we infected monocytes from both healthy elderly individuals (a tuberculosis susceptibility group) and elderly tuberculosis patients with M. tuberculosis, and performed a microarray experiment. We detected 78 differentially expressed transcripts and confirmed these results by quantitative PCR of selected genes. We found that monocytes from tuberculosis patients showed similar expression patterns for these genes, regardless of whether they were obtained from younger or older patients. Only one of the detected genes corresponded to a cytokine: IL26, a member of the interleukin-10 (IL-10) cytokine family which we found to be down-regulated in infected monocytes from tuberculosis patients. Non-infected monocytes secreted IL-26 constitutively but they reacted strongly to M. tuberculosis infection by decreasing IL-26 production. Furthermore, IL-26 serum concentrations appeared to be lower in the tuberculosis patients. When whole blood was infected, IL-26 inhibited the observed pathogen-killing capability. Although lymphocytes expressed IL26R, the receptor mRNA was not detected in either monocytes or neutrophils, suggesting that the inhibition of anti-mycobacterial activity may be mediated by lymphocytes. Additionally, IL-2 concentrations in infected blood were lower in the presence of IL-26. The negative influence of IL-26 on the anti-mycobacterial activity and its constitutive presence in both serum and monocyte supernatants prompt us to propose IL26 as a candidate gene for tuberculosis susceptibility.

Macrophages from elders are more permissive to intracellular multiplication of Mycobacterium tuberculosis.

The elderly account for a disproportionate share of all tuberculosis cases, and the population ageing may not fully explain this phenomenon. We have performed in vitro infection experiments to investigate whether there is an immunological basis for the apparent susceptibility of elders to tuberculosis. In our infection model, Mycobacterium tuberculosis induces a higher production of interleukin (IL)-6 and reactive oxygen species in macrophages from elders than from younger adults. This response did not prevent, however, an increased multiplication of M. tuberculosis in macrophages from elders as compared with the growth observed within cells from adults. By performing a factorial experiment, we have found that IFN-γ, but not IL-1ß, IL-6 or TNF-α, stimulate the macrophages to restrict the multiplication of the bacterium in macrophages from elders. Although monocytes from elders seem to be in a higher level of activation, we present evidences that protein tyrosine phosphorylation response induced by M. tuberculosis is stronger in monocytes from adults than from elders. Using a protein array that detects 71 tyrosine phosphorylated kinases, we identified Pyk2 as the only kinase that displayed a difference of intensity larger than 50 % in adults than in elders. Furthermore, monocytes from elders that were incubated in the presence of tyrosine kinase inhibitors (genistein and PP2) allowed a higher level of bacterial multiplication. These observations may help to explain the susceptibility of elders to tuberculosis. An unexpected result was that both genistein and its negative control, daidzein, abundant soy isoflavones, promoted intracellular mycobacterial growth.

Delineation of commonly deleted chromosomal regions in meningiomas by high-density single nucleotide polymorphism genotyping arrays.

Despite recent advances in the identification of the cytogenetic profiles of meningiomas, a significant group of tumors still show normal karyotypes or few chromosomal changes. The authors analyzed the cytogenetic profile of 50 meningiomas using fluorescence in situ hybridization and high-density (500 K) single nucleotide polymorphism (SNP) arrays. Our results confirm that del(22q) (52%) and del(1p) (16%) (common deleted regions: 22q11.21-22q13.3. and 1p31.2-p36.33) are the most frequent alterations. Additionally, recurrent monosomy 14 (8%), del(6q) (10%), del(7p) (10%), and del(19q) (4%) were observed, while copy number patterns consistent with recurrent chromosomal gains, gene amplification, and copy number neutral loss of heterozygosity (cnLOH) were either absent or rare. Based on their overall SNP profiles, meningiomas could be classified into: (i) diploid cases, (ii) meningiomas with a single chromosomal change [e.g., monosomy 22/del(22q)] and (iii) tumors with ≥2 altered chromosomes. In summary, our results confirm and extend on previous observations showing that the most recurrent chromosomal abnormalities in meningiomas correspond to chromosome losses localized in chromosomes 1, 22 and less frequently in chromosomes 6, 7, 14, and 19, while chromosomal gains and cnLOH are restricted to a small proportion of cases. Finally, a set of cancer-associated candidate genes associated with the TP53, MYC, CASP3, HDAC1, and TERT signaling pathways was identified, in cases with coexisting monosomy 14 and del(1p).

Linfoma intestinal de células T asociado a enteropatía y sin relación con enfermedad celíaca / Enteropathy-associated intestinal t-cell lymphoma without celiac disease

La enteropatía asociada a linfoma de células T tipo II es un linfoma intestinal infrequente. Presentamos el caso un varón de 73 años con diarrea y pérdida de peso. La biopsia duodenal presentaba atrofia e infiltrado de linfocitos irregulares. La inmunohistoquímica detectó positividad para CD3, CD8, CD56 con reordenamiento monoclonal del TCR. El genotipifación de HLA-DQ era DQ5/DQ9. El test para EBVRNA fue negativo. Antes del tratamiento específico quimioterápico ingresó por infección respiratoria, y falleció por causa independiente del linfoma. El diagnóstico diferencial de los procesos linfoproliferativos CD56-positivo incluye EATL tipo II, linfoma intestinal primario de células T/NK y linfoma de células T hepatoesplénico.El paciente presentaba CD8 y CD56+ marcadores que permiten descartar EALT tipo I. la genotipificación HLA-DQ no corresponde a enfermedad celíaca, y la biopsia presentaba proliferación de linfocitos con atipias. El linfoma intestinal primario de células T/NK se caracteriza principalmente por ausencia de CD8 y del reordenamiento monoclonal del TCR presentes en este caso(AU)

Type II enteropathy-associated T-cell lymphoma (EATL) is an uncommon intestinal lymphoma. We report the case of a 73-year-old man with diarrhea and weight loss. Duodenal biopsy showed atrophy and infiltration of irregular lymphocytes. Immunohistochemistry was positive for CD3, CD8, and CD56 with monoclonal TCR rearrangement. The HLA-DQ genotype was DQ5/DQ9. The Epstein-Barr virus RNA test was negative. Before specific chemotherapy could be administered, the patient was admitted to hospital for a respiratory infection and died from a cause unrelated to his lymphoma. The differential diagnosis of CD56-positive lymphoproliferative processes include type II EATL, primary T-cell/natural killer-cell intestinal lymphoma and hepatosplenic T-cell lymphoma. The patient had CD8 y CD56+ markers that allowed type I EATL to be excluded. The HLA-DQ genotype did not correspond to celiac disease and the biopsy showed proliferation of lymphocytes with atypia. The primary intestinal T-cell/natural killer-cell lymphoma was characterized mainly by the absence of CD8 and monoclonal reassortment of the TCR present in this case (AU)

Non-chemotactic influence of CXCL7 on human phagocytes. Modulation of antimicrobial activity against L. pneumophila.

We have investigated the role of CXCL7 in the immune response of human phagocytes against the intracellular bacteria Mycobacterium tuberculosis and Legionella pneumophila. We have observed that polymorphonuclear neutrophil (PMN) chemotaxis induced by the supernatants of infected monocyte derived macrophages (MDM) may be attributed to CXCL8 rather than CXCL7, although both chemokines are present in large quantities. We have also found that CXCL7 is present not only in the supernatants of MDM, but also in the supernatants of PMN of some, but not all, individuals. Western blot analysis revealed that, in both MDM and PMN supernatants appeared two bands with molecular weights consistent with the platelet basic protein (PBP) and the neutrophil activating protein-2 (NAP-2) sizes. Regarding the influence on infected cells, recombinant NAP-2 enhanced the antimicrobial activity of IFNγ activated MDM against L. pneumophila, but not against M. tuberculosis. In addition, U937 cells transfected with a NAP-2 construct inhibited the intracellular multiplication of L. pneumophila, supporting its role in the modulation of the antimicrobial activity. Finally, U937 cells transfected with the NAP-2 construct showed an adherence that was dramatically enhanced when the substrate was fibronectin. We conclude that human phagocytes produce CXCL7 variants that may have a significant influence on the immune response against bacterial pathogens.

[Enteropathy-associated intestinal t-cell lymphoma without celiac disease]. / Linfoma intestinal de células T asociado a enteropatía y sin relación con enfermedad celíaca.

Type II enteropathy-associated T-cell lymphoma (EATL) is an uncommon intestinal lymphoma. We report the case of a 73-year-old man with diarrhea and weight loss. Duodenal biopsy showed atrophy and infiltration of irregular lymphocytes. Immunohistochemistry was positive for CD3, CD8, and CD56 with monoclonal TCR rearrangement. The HLA-DQ genotype was DQ5/DQ9. The Epstein-Barr virus RNA test was negative. Before specific chemotherapy could be administered, the patient was admitted to hospital for a respiratory infection and died from a cause unrelated to his lymphoma. The differential diagnosis of CD56-positive lymphoproliferative processes include type II EATL, primary T-cell/natural killer-cell intestinal lymphoma and hepatosplenic T-cell lymphoma. The patient had CD8 y CD56+ markers that allowed type I EATL to be excluded. The HLA-DQ genotype did not correspond to celiac disease and the biopsy showed proliferation of lymphocytes with atypia. The primary intestinal T-cell/natural killer-cell lymphoma was characterized mainly by the absence of CD8 and monoclonal reassortment of the TCR present in this case.

Research resource: Transcriptional profiling reveals different pseudohypoxic signatures in SDHB and VHL-related pheochromocytomas.

The six major genes involved in hereditary susceptibility for pheochromocytoma (PCC)/paraganglioma (PGL) (RET, VHL, NF1, SDHB, SDHC, and SDHD) have been recently integrated into the same neuronal apoptotic pathway where mutations in any of these genes lead to cell death. In this model, prolyl hydroxylase 3 (EglN3) abrogation plays a pivotal role, but the molecular mechanisms underlying its inactivation are currently unknown. The aim of the study was to decipher specific alterations associated with the different genetic classes of PCCs/PGLs. With this purpose, 84 genetically characterized tumors were analyzed by means of transcriptional profiling. The analysis revealed a hypoxia-inducible factor (HIF)-related signature common to succinate dehydrogenase (SDH) and von Hippel-Lindau (VHL) tumors, that differentiated them from RET and neurofibromatosis type 1 cases. Both canonical HIF-1α and HIF-2α target genes were overexpressed in the SDH/VHL cluster, suggesting that a global HIF deregulation accounts for this common profile. Nevertheless, when we compared VHL tumors with SDHB cases, which often exhibit a malignant behavior, we found that HIF-1α target genes showed a predominant activation in the VHL PCCs. Expression data from 67 HIF target genes was sufficient to cluster SDHB and VHL tumors into two different groups, demonstrating different pseudo-hypoxic signatures. In addition, VHL-mutated tumors showed an unexpected overexpression of EglN3 mRNA that did not lead to significantly different EglN3 protein levels. These findings pave the way for more specific therapeutic approaches for malignant PCCs/PGLs management based on the patient's genetic alteration.

Apoptosis and oxidative burst in neutrophils infected with Mycobacterium spp.

Two of the better characterized antimicrobial mechanisms displayed by human neutrophils are the reactive oxygen species (ROS) production and the induction of apoptosis. Their importance in mycobacterial infections is, however, controversial and we aimed to analyze them simultaneously in neutrophils infected with either Mycobacterium tuberculosis or the non-pathogenic M. gordonae. Neither species is eliminated by neutrophils but the pattern exhibited for both activities is completely different. M. tuberculosis induces ROS production and apoptosis but M. gordonae does not. Additional evidence was provided by an attenuated strain of M. gordonae that, although it has become susceptible to the antimicrobial activity of neutrophils, it still does not promote ROS production or apoptosis. Therefore no relationship could be established between any of these activities and the ability of neutrophils to kill mycobacteria. We have also observed that neutrophil concentration, a variable that is important in the antimicrobial activity against other pathogens, has no influence in the mycobacterial intracellular growth.