Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus from a symbiotic bacterium, a bacterium living in close physical association with another organism.

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

Any process that activates or increases the frequency, rate or extent of the chemical reactions and pathways resulting in the breakdown of a protein by the destruction of the native, active configuration, with or without the hydrolysis of peptide bonds.

Any process that stops, prevents, or reduces the frequency, rate or extent of complement activation by the classical pathway.

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

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.

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.

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

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.