Cell Surface vs. Soluble Extracellular Communication Molecules

The immune system relies on a complex network of ligands and receptors for communication. Here are examples of various types of ligands and receptors involved in immune system signaling:

Cell Surface Ligands:

1. Major Histocompatibility Complex (MHC) molecules:
   • These cell surface proteins present antigens to T cells, playing a crucial role in the adaptive immune response.
2. CD (Cluster of Differentiation) proteins:
   • Examples include CD4 and CD8, which serve as co-receptors on T cells and are involved in interactions with antigen-presenting cells.

Secreted and Cleaved Ligands:

1. Cytokines:
   • Examples include interleukins (ILs), interferons (IFNs), and tumor necrosis factor (TNF). These signaling proteins are secreted and act as messengers between immune cells.
2. Chemokines:
   • These secreted signaling proteins play a role in chemotaxis, guiding immune cells to specific locations in the body.

Cell Surface Receptors:

1. Toll-like Receptors (TLRs):
   • These receptors are located on the surface of immune cells and recognize specific molecular patterns associated with pathogens, initiating an immune response.
2. B Cell Receptors (BCRs) and T Cell Receptors (TCRs):
   • BCRs are present on the surface of B cells and recognize antigens directly, while TCRs on T cells interact with antigens presented on MHC molecules.

Secreted and Cleaved Receptors:

1. Soluble Interleukin-2 Receptor (sIL-2R):
   • This is a cleaved form of the IL-2 receptor that is released into the bloodstream. It can serve as a biomarker for immune system activation.
2. Soluble Tumor Necrosis Factor Receptor (sTNFR):
   • This is a cleaved form of the TNF receptor that can be released into the extracellular space. It acts as a decoy receptor for TNF, regulating its activity.

These examples illustrate the diversity of ligands and receptors involved in immune system signaling, allowing for precise and coordinated responses to various pathogens and challenges. The interactions between these molecules play a crucial role in immune surveillance, activation, and regulation.

Next Topic: An Alphanumeric Soup of Cytokine and Cytokine Receptor Families

Source: ChatGPT response prompted and edited by Joel Graff.

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