Lymphocyte subsets in Atlantic cod (Gadus morhua) interrogated by single-cell sequencing
Naomi Croft Guslund, Anders K. Krabberød, Simen Foyn Nørstebø, Monica Hongrø Solbakken, Kjetill S. Jakobsen, Finn–Eirik Johansen, Shuo‐Wang Qiao
Abstract
Atlantic Cod (Gadus morhua) has lost the major histocompatibility complex class II presentation pathway. We recently identified CD8-positive T cells, B cells, and plasma cells in cod, but further characterisation of lymphocyte subsets is needed to elucidate immune adaptations triggered by the absence of CD4-positive T lymphocytes. Here, we use single-cell RNA sequencing to examine the lymphocyte heterogeneity in Atlantic cod spleen. We describe five T cell subsets and eight B cell subsets and propose a B cell trajectory of differentiation. Notably, we identify a subpopulation of T cells that are CD8-negative. Most of the CD8-negative T lymphocytes highly express the homologue of monocyte chemotactic protein 1b, and another subset of CD8-negative T lymphocytes express the homologue of the scavenger receptor m130. Uncovering the multiple lymphocyte cell sub-clusters reveals the different immune states present within the B and T cell populations, building a foundation for further work.