Probable B cell-associated cytokine that plays a role in the regulation of humoral immune responses (PubMed:28978694). Involved in lymphocyte B cell development and immunoglobulin/IgA production (PubMed:28978694). Expressed in bone marrow, spleen and lymph node (PubMed:28978694). Up-regulated in the mammary gland upon the onset of lactation (PubMed:28978694). Up-regulated in peripheral blood lymphocyte B cells upon activation (PubMed:28978694). Mice are viable and reproduce normally (PubMed:28978694). Show reduced number of both peripheral lymphocyte B cells in the spleen and precursor and mature lymphocyte B cells in the bone marrow (PubMed:28978694). Show smaller and fewer Peyer's patches, lower numbers of immunoglobulin/IgA-secreting B cells and an altered gut microbiome (PubMed:28978694). Exhibit reduced levels of immunoglobulin/IgA in the serum, gut, feces, and lactating mammary gland (PubMed:28978694).