The solute carrier family 6 member 4 (SLC6A4), also known as the serotonin transporter (5-HTT), is a transmembrane protein responsible for the reuptake of serotonin (5-HT) from synaptic clefts, regulating serotonergic neurotransmission. It plays a critical role in mood regulation, anxiety, and stress responses, with polymorphisms in the SLC6A4 gene (e.g., 5-HTTLPR) linked to psychiatric disorders such as depression, obsessive-compulsive disorder, and post-traumatic stress disorder. Antibodies targeting SLC6A4 are essential tools for studying its expression, localization, and function in both research and clinical contexts. These antibodies, often raised in rabbits or mice, enable techniques like immunohistochemistry, Western blotting, and immunofluorescence to visualize SLC6A4 distribution in brain tissues, peripheral blood cells, or transfected cell models. Specificity validation (e.g., knockout controls) is crucial due to potential cross-reactivity with related transporters. Research using SLC6A4 antibodies has provided insights into altered transporter density in psychiatric conditions, effects of antidepressants (e.g., SSRIs), and neurodevelopmental changes. Recent applications extend to investigating gut-brain axis interactions, as SLC6A4 is also expressed in enterocytes. However, variability in antibody performance across species or fixation methods requires careful experimental optimization.