Understanding fish B cell responses to combat infectious diseases

Abstract

Teleost fish possess all the necessary elements to mount an adaptive immune response, yet, the many physiological and structural differences between the mammalian and the teleost adaptive immune system, anticipate significant changes regarding how this response is coordinated and executed. As a result, the adaptive response in fish is often slower and weaker than that of mammals. B cells are key players in adaptive immune responses through the production of antibodies. Nonetheless, recent studies performed in mammals and other species including fish point to many additional functions of B cells within both the adaptive and the innate immune system, in many occasions taking part in the crosstalk between these two arms of the immune response. Furthermore, it should be taken into consideration that fish B cells share many functional and phenotypical features with mammalian innate B cell populations, also greatly conditioning their response to pathogens. Our knowledge regarding B cell function in fish has increased greatly in the past years, studies that have allowed us for example to identify different subsets of B cells, detect specific antibody-secreting cells or even establish the transcriptomic profile and the B cell receptor sequence of single cells in different stages of differentiation. In the current work, we will summarize what is currently known regarding fish B cells, knowledge that is essential for the future design of novel strategies to combat infectious diseases.