Lipopolysaccharides (LPS) are the main components of the external leaflet of the Gram-negative outer membrane and consist of three different moieties: lipid A, core oligosaccharide, and O-polysaccharide.

The lipid A is a glucosamine disaccharide with different levels of acylation and phosphorylation, beside carrying, in certain cases, additional substituents on the sugar backbone. It is also the main immunostimulatory part of the LPS, as its recognition by the host immune system represents a fundamental event for detection of perilous microorganisms. However, an uncontrolled immune response caused by a large amount of circulating LPS can lead to dramatic outcomes for human health, such as septic shock. The immunostimulant properties of an LPS incredibly vary depending on lipid A chemical structure, and for this reason, natural and synthetic variants of the lipid A are under study to develop new drugs that mimic or antagonise its natural effects. Here, we review past and recent findings on the lipid A as a drug target and immune-therapeutic molecule, with a special attention on the crucial role of the chemical structure and its exploitation for conceiving novel strategies for treatment of several immune-related related pathologies.

脂多糖 (LPS) 是革兰氏阴性菌外膜外叶的主要成分，由三个不同的部分组成：脂质 A、核心寡糖和 O-多糖。

脂质 A 是一种具有不同水平的酰化和磷酸化的葡糖胺二糖，除了在某些情况下在糖骨架上携带额外的取代基之外。它也是 LPS 的主要免疫刺激部分，因为它被宿主免疫系统识别代表了检测危险微生物的基本事件。然而，由大量循环 LPS 引起的不受控制的免疫反应会导致人类健康的严重后果，例如感染性休克。LPS 的免疫刺激特性因脂质 A 的化学结构而异，因此，正在研究脂质 A 的天然和合成变体，以开发模拟或拮抗其自然作用的新药。这里，