This MAb recognizes a protein of 36 kDa, identified as ICOS-L. It is a ligand for the ICOS receptor that initiates T and B cell proliferation and cytokine secretion. ICOS-L interactions play an essential role in T cell-dependent B cell activation in peripheral lymphoid organs such as spleen and lymph nodes. ICOS-L protein is present in myeloid leukocytes, and by Northern blot there are 2. 4, 3. 0, and 7. 0 kb transcripts in brain, heart, kidney, and liver, with lower expression in colon and thymus, and a 1. 1 kb transcript in leukocytes. Tumor necrosis factor alpha (TNF), granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) enhance its expression. LPS-induced up-regulation of ICOS-L is dependent on the MyD88-dependent signaling pathway. Primary antibodies are available purified, or with a selection of fluorescent CF® Dyes and other labels. CF® Dyes offer exceptional brightness and photostability. Note: Conjugates of blue fluorescent dyes like CF®405S and CF®405M are not recommended for detecting low abundance targets, because blue dyes have lower fluorescence and can give higher non-specific background than other dye colors.