The STK39 antibody targets the serine/threonine kinase 39 (STK39), also known as SPAK (STE20/SPS1-related proline-alanine-rich kinase), a protein encoded by the *STK39* gene in humans. STK39 is a member of the STE20 kinase family and plays a critical role in cellular responses to osmotic stress, ion transport regulation, and blood pressure homeostasis. It interacts with cation-chloride cotransporters (e.g., NKCC1. NKCC2) and the WNK kinase pathway, modulating their activity via phosphorylation. Dysregulation of STK39 has been linked to hypertension, neurological disorders, and cancer progression. Antibodies against STK39 are essential tools for studying its expression, localization, and function in tissues or cell lines. They are widely used in techniques like Western blotting, immunohistochemistry, and immunofluorescence. Research applications include exploring STK39's role in salt-sensitive hypertension, neuronal excitability, and cellular stress signaling. Commercial STK39 antibodies are typically validated for specificity using knockout controls or siRNA-mediated knockdown. Both monoclonal and polyclonal variants are available, often targeting conserved regions such as the kinase domain or N-terminal regulatory sequences. Reliable STK39 antibodies are critical for elucidating its physiological and pathological mechanisms.