## 1 Introduction  
Coffee is one of the most commonly consumed beverages in the world [1]. For many populations, coffee is the major source of caffeine [1], the most widely consumed psychostimulant [2]. However, coffee is also a very rich source of chlorogenic acids (CGAs), naturally-produced phenolic acids that are derived from the esterification of cinnamic acids and quinic acid [3]. The most abundant CGA in coffee is 5-caffeoylquinic acid (5-CQA), which accounts for approximately 80% of the total CGA content [4]. Furthermore, coffee is the main source of CGAs in the human diet, with less contribution provided from other products such as tea and some fruits and vegetables [5].  
It has been reported that a regular intake of coffee is associated with a reduced risk of chronic diseases, such as type 2 diabetes [6, 7], metabolic syndrome [8], cardiovascular diseases [9, 10], and cancer [10]. Furthermore, consumption of coffee has been recently associated with lower all-cause cancer mortality [11]. Interestingly, some studies have shown an anti-inflammatory effect of regular coffee consumption [12, 13, 14, 15].  
Due to having antioxidant and anti-inflammatory properties, the health benefits of coffee have been attributed, at least in part, to CGAs [3; 14; 16]. Studies testing the anti-inflammatory activity of CGAs are scarce, but some have confirmed this anti-inflammatory effect [3]. Two studies carried out with mouse macrophages demonstrated how the presence of 5-CQA (the CGA most commonly tested), in cell culture suppressed the lipopolysaccharide-charide (LPS)-stimulated production of pro-inflammatory compounds [17; 18]. On the other hand, studies in animal models have shown that the administration of 5-CQA causes suppresses in the circulating levels of pro-inflammatory cytokines [19; 20; 21]. However, no studies using human cells, particularly blood cells, focused on to analyzing the possible anti-inflammatory effect of chlorogenic acids currently exist in the literature. Furthermore, in some studies, the 5-CQA concentrations used were in the \(\upmu\)M range [17; 18], whereas concentrations observed in human plasma after coffee ingestion are typically in the nM range [22]. Therefore, it would be of interest to analyze the anti-inflammatory effect of 5-CQA, as it is the most abundant CGA in coffee, using human blood cells stimulated with LPS, a commonly used model.  
However, the potential effects of caffeine should also be considered. Caffeine can interact with almost all tissues in the organism, including the immune system [23]. In this regard, a number of animal and in vitro studies have been focused on the effects of caffeine on immune related parameters, such as tumor necrosis factor (TNF)-\(\upalpha\) and antibody production, hypersensitivity and natural killer cell cytotoxicity, indicating an anti-inflammatory role for caffeine [23]. As such, some studies have reported that caffeine suppresses TNF-\(\upalpha\) production in vitro [24; 25], but only when caffeine concentrations are higher than the physiological ones.  
Taking into account these considerations, the aim of the present study was to determine the effect of caffeine and 5-CQA, using physiological concentrations comparable to typical human consumption, on the LPS-induced cytokine production in whole blood in vitro cultures. Due to the low concentrations tested, limited effects of caffeine and 5-CQA on cytokine production are expected.