先天免疫反应可提供第一道防线，对抗常见的微生物；而在更复杂和/或反复出现的病原体情况下，适应性免疫反应已逐渐进化，可提供更好的保护，以应对随后的感染。然而，这种二分法必须重新评估，因为已经发现，先天性B细胞（例如B1和边缘区B细胞）和新发现的先天淋巴细胞（iLC）表现出先天性质的特点，如抗原内化，调节性B细胞功能和辅助T细胞活性。此外，由先天性B细胞产生和功能的天然抗体（nAbs），以及它们激活经典补体途径的能力，构成了先天和适应性免疫的重要机制，以及近期在先天性免疫范围内加入血小板的整合。毫无疑问，这些机制在免疫和稳态中特别在生命的最初几年中具有优势，但是在各种自身免疫性/炎症性疾病，过敏和癌症以及对免疫治疗的反应中，人们开始考虑这些前体可能产生不良影响。因此，正如在本期《临床变态反应与免疫学评论》中所提出的，深入理解介于先天和适应性免疫反应交汇处的关键分子和细胞因子涉及到我们对免疫和免疫病理反应的理解是一个新的挑战。

The innate immune response provides a first line of defense against common microorganisms and, for more complex and/or recurring situations where pathogens must be eliminated, an adaptive immune response has emerged and evolved to provide better protection against subsequent infections. However, such dichotomy has to be reevaluated because innate B cells (e.g., B1 and marginal zone B cells) and the newly described innate lymphoid cells (iLC) have been found to exhibit innate-like properties, such as antigen internalization, regulatory B cell functions, and helper T cell activities. In addition, the production and function of natural antibodies (nAbs) by innate B cells and their capacity to activate the classical complement pathway constitute additional important mechanisms at the junction of innate and adaptive immunity as well as the recent integration of platelets into the innate immune spectrum. There is no doubt that these mechanisms present an advantage in immunity and homeostasis particularly during the first years of life, but arguments are arising to consider that these precursors may have detrimental effects in a variety of autoimmune/inflammatory diseases, allergies and cancers, as well as in response to immunotherapy. Accordingly, and as presented in this special issue of Clinical Reviews in Allergy and Immunology, a better comprehension of the key molecular and cellular actors implicated at the crossroads of the innate and adaptive immune response represents a new challenge in our understanding of the immunological and immunopathological responses.