The immune system is a collection of cells, tissues, and organs in the body that defend against attacks by "foreign" invaders. Once the invader is recognized, the immune response is triggered. T cells become activated after recognizing major histocompatibility complex (MHC) molecules on antigen-presenting cells (APCs) with the T cell receptor and co-signaling molecules. The immune system has its own immunoregulators, referred to as immune checkpoints. The immune checkpoint molecules have both positive and negative modulatory effects on T cell activation. Immune checkpoint therapies, targeting regulatory pathways in T cells to enhance antitumor immunity, are the focus of research on the treatment of several forms of cancer. Due to the dynamic nature of the immune response and multifaceted regulation of immune signaling pathways, immunity can overshoot its targets and attack healthy tissues or organs after release from checkpoint arrest. The way forward for immune checkpoint therapy lies in better understanding of the interaction between the immune system and tumor cells.

Immune checkpoint antibody targets


Invitrogen immune checkpoint antibodies are designed to dependably detect the key research targets. Each antibody is validated for use in various applications.

Immunofluorescence analysis of DR3/TNFRSF25

Immunofluorescence analysis of DR3/TNFRSF25. The experiment was performed on fixed and permeabilized Ramos cells for detection of endogenous DR3/TNFRSF25 using using DR3 Recombinant Rabbit Monoclonal Antibody (11H6L9) (Cat. No. 702277, 2 μg/mL) and labeled with Goat anti–Rabbit IgG (H+L) Superclonal Recombinant Secondary Antibody, Alexa Fluor 488 (Cat. No. A27034, 1:2,000). Panel a shows representative cells that were stained for detection and localization of DR3/TNFRSF25 protein (green); panel b is stained for nuclei (blue) using SlowFade Gold Antifade Mountant with DAPI (Cat. No. S36938); panel c represents cytoskeletal F-actin staining using Rhodamine Phalloidin (Cat. No. R415, 1:300); panel d is a composite image of panels a, b, and c clearly demonstrating localization of DR3/TNFRSF25 in the membrane. The images were captured at 60x magnification.

Flow cytometry analysis of Galectin-9. Mouse thymocytes were stained with Galectin-9 Short Polyclonal Antibody (Cat. No. PA5-47503) (orange histogram) or control antibody (open histogram), followed by an APC-conjugated anti–rat IgG secondary antibody. To facilitate intracellular staining, cells were fixed with paraformaldehyde and permeabilized with saponin.

Flow cytometry analysis of galectin-9
Immunohistochemical analysis of galectin-9

Immunohistochemical analysis of Galectin-9. The target was detected in perfusion-fixed and frozen sections of mouse colon using Galectin-9 Monoclonal Antibody (766428) (Cat. No. MA5-24369) at 25 μg/mL overnight at 4°C. The tissue was stained using an anti-rat IgG secondary antibody, HRP conjugate, with DAB substrate (brown), and counterstained with hematoxylin (blue). Specific staining was localized to plasma membranes and cytoplasm of epithelial cells.