An endocytosis process in which cell surface receptors ensure specificity of transport. A specific receptor on the cell surface binds tightly to the extracellular macromolecule (the ligand) that it recognizes; the plasma-membrane region containing the receptor-ligand complex then undergoes endocytosis, forming a transport vesicle containing the receptor-ligand complex and excluding most other plasma-membrane proteins. Receptor-mediated endocytosis generally occurs via clathrin-coated pits and vesicles.

Any process involved in the activation of any of the steps of the complement cascade, which allows for the direct killing of microbes, the disposal of immune complexes, and the regulation of other immune processes; the initial steps of complement activation involve one of three pathways, the classical pathway, the alternative pathway, and the lectin pathway, all of which lead to the terminal complement pathway.

Any process involved in the activation of any of the steps of the classical pathway of the complement cascade which allows for the direct killing of microbes, the disposal of immune complexes, and the regulation of other immune processes.

Any process that modulates the frequency, rate or extent of complement activation.

A series of molecular signals initiated by the binding of the Fc portion of immunoglobulin E (IgE) to an Fc-epsilon receptor on the surface of a signal-receiving cell, and ending with regulation of a downstream cellular process, e.g. transcription. The Fc portion of an immunoglobulin is its C-terminal constant region.

An Fc-gamma receptor signaling pathway that contributes to the endocytic engulfment of external particulate material by phagocytes.

Any process that modulates the frequency, rate or extent of the immune response, the immunological reaction of an organism to an immunogenic stimulus.

The movement of a leukocyte within or between different tissues and organs of the body.

Any immune system process that functions in the calibrated response of an organism to a potential internal or invasive threat.

The process in which plasma is filtered through the glomerular membrane which consists of capillary endothelial cells, the basement membrane, and epithelial cells. The glomerular filtrate is the same as plasma except it has no significant amount of protein.

An immune response against bacteria mediated through a body fluid. Examples of this process are the antibacterial humoral responses in Mus musculus and Drosophila melanogaster.

The space external to the outermost structure of a cell. For cells without external protective or external encapsulating structures this refers to space outside of the plasma membrane. This term covers the host cell environment outside an intracellular parasite.

The membrane surrounding a cell that separates the cell from its external environment. It consists of a phospholipid bilayer and associated proteins.

The space external to the outermost structure of a cell. For cells without external protective or external encapsulating structures this refers to space outside of the plasma membrane. This term covers the host cell environment outside an intracellular parasite.

A phospholipid microvesicle that is derived from any of several cell types, such as platelets, blood cells, endothelial cells, or others, and contains membrane receptors as well as other proteins characteristic of the parental cell. Microparticles are heterogeneous in size, and are characterized as microvesicles free of nucleic acids.

A vesicle that is released into the extracellular region by fusion of the limiting endosomal membrane of a multivesicular body with the plasma membrane. Extracellular exosomes, also simply called exosomes, have a diameter of about 40-100 nm.

That part of a multicellular organism outside the cells proper, usually taken to be outside the plasma membranes, and occupied by fluid.

That part of a multicellular organism outside the cells proper, usually taken to be outside the plasma membranes, and occupied by fluid.

A protein complex composed of two identical immunoglobulin heavy chains of an IgA isotype and two identical immunoglobulin light chains, held together by disulfide bonds, and present in the extracellular space, in mucosal areas or other tissues, or circulating in the blood or lymph.

A polymeric IgA immunoglobulin complex that is complexed with one chain of secretory component (SC). Polymeric IgA is present in mucosal areas, having been transported via a transcytosis mechanism in mucosal epithelial cells relying on the polymeric Ig receptor, a portion of which then remains bound to the polymeric IgA as secretory component.

A circulating form of IgM consisting of a pentamer of IgM core units with a single J chain polypeptide.