BACKGROUND CD64 (FcγR1) is a high-affinity receptor for monomeric IgG1 and IgG3. Circulating neutrophils express very low amounts of CD64 on their surface. OBJECTIVES Our primary aim was to investigate the utility of neutrophil CD64 surface expression as a biomarker of active pulmonary tuberculosis (TB). We hypothesised that elevated neutrophil CD64 expression in TB infection would be associated with interferon gamma (IFN-γ) as an inducer of CD64 expression. METHODS The expression level of CD64 per neutrophil (PMN CD64 index) was quantitatively measured with flow cytometry using a Leuko64 kit in samples from patients with TB and latent TB infection (LTBI) as well as healthy controls, as part of a prospective cohort study in Brazil. FINDINGS The PMN CD64 index in patients with TB was higher than that in healthy controls and LTBI. Receiver operating characteristic curve analyses determined that the PMN CD64 index could discriminate patients with TB from those with LTBI and healthy individuals. PMN CD64 index levels returned to baseline levels after treatment. CONCLUSIONS The positive regulation of CD64 expression in circulating neutrophils of patients with active TB could represent an additional biomarker for diagnosis of active TB and could be used for monitoring individuals with LTBI before progression of TB disease.

INTRODUÇÃO: Leptospirose é uma zoonose que permanece endêmica em regiões tropicais e temperadas. A dificuldade no diagnóstico clínico diferencial entre os quadros de leptospirose humana e as várias arboviroses (dengue, febre amarela, febre de oropouche), febre maculosa brasileira, hepatite viral e hantavirose permanece um problema na Saúde Pública. MÉTODOS: No presente estudo, foi realizada análise retrospectiva de características demográficas, epidemiológicas, clínicas e laboratoriais de 27 casos de leptospirose humana que ocorrerem durante um período de 13 anos sem ocorrência de notificação de surtos epidêmicos no Rio de Janeiro, Brasil (1996-2009). RESULTADOS: A mortalidade da coorte de pacientes com leptospirose correspondeu a 11,1%, sem embargo, o grupo de pacientes com atipia linfocitária não evoluiu para o óbito (OR = 11,1; 95% CI = 1,12-110,9; p = 0.04). Em duas oportunidades, foi observada uma expansão dos linfócitos T gama-delta no sangue periférico de pacientes na fase septicêmica da leptospirose. CONCLUSÕES: Atipia linfocitária pode ocorrer em pacientes com leptospirose. Nossos dados também sugerem que os linfócitos atípicos podem estar envolvidos na patogênese da leptospirose.

INTRODUCTION: Leptospirosis is a zoonotic disease found in tropical and temperate countries, and its clinical diagnostic confusion with arboviruses (dengue fever, oropouche fever and yellow fever), Brazilian spotted fever, viral hepatitis and hantaviruses has been an ongoing public health concern. The aim of this observational study was to demonstrate an association between findings of atypical lymphocytosis and the progression of endemic leptospirosis. METHODS: A retrospective analysis was performed on the demographic, epidemiological, clinical and laboratory aspects of 27 human leptospirosis cases that occurred over a period of 13 years (1996-2009) with no reported epidemic outbreaks in Rio de Janeiro, Brazil. RESULTS: The overall mortality rate was 11.1% in our cohort of hospitalized cases. However, there was no mortality among patients with atypical lymphocytosis (OR = 11.1; 95% CI = 1.12-110.9; p = 0.04). Two patients who were in the septicemic phase showed signs of expansion of γδ T cell responses in peripheral blood. CONCLUSIONS: Atypical lymphocytosis may be observed in patients with leptospirosis. Our observations suggest that these atypical leukocyte subsets are associated with partial protection during the disease course of leptospirosis.