Teleost IgM+ plasma-like cells: beyond antibody secretion

Area of Science:

• Immunology
• Fish Biology
• Cellular Differentiation

Background:

• Antibody-secreting cells (ASCs) differentiate from B cells to produce antibodies, typically losing other B cell functions.
• Teleost fish B cells share traits with mammalian B1 innate subsets, but their ASC differentiation is poorly understood.

Purpose of the Study:

• Investigate the functionalities of ASCs in teleost fish, using rainbow trout (Oncorhynchus mykiss) as a model.
• Characterize the differentiation process of teleost B cells and their retained capabilities.

Main Methods:

• Isolated IgM+ plasma-like cells from rainbow trout head kidney.
• Assessed IgM secretion, phagocytic and antigen-presenting capacities in vitro.
• Evaluated B cell receptor functionality using thymus-independent antigens and crosslinking.

Main Results:

• Rainbow trout IgM+ plasma-like cells exhibit high IgM secretion, phagocytosis, and antigen presentation, exceeding naive B cells.
• These cells survived for 2 weeks in vitro while secreting IgM.
• A functional B cell receptor was observed, responding to antigens and crosslinking stimuli.

Conclusions:

• Teleost plasma-like cells retain B cell receptor functionality and antigen-presenting capabilities beyond antibody secretion.
• This suggests a unique teleost B cell differentiation pathway distinct from mammals.
• Findings offer insights into the differentiation of mammalian innate-like B cells, such as B1 cells.