Any process in which an organism activates, maintains or increases the frequency, rate or extent of the immune response of the host organism; the immune response is any immune system process that functions in the calibrated response of an organism to a potential internal or invasive threat. The host is defined as the larger of the organisms involved in a symbiotic interaction.

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

The rigid or semi-rigid envelope lying outside the cell membrane of plant, fungal, most prokaryotic cells and some protozoan parasites, maintaining their shape and protecting them from osmotic lysis. In plants it is made of cellulose and, often, lignin; in fungi it is composed largely of polysaccharides; in bacteria it is composed of peptidoglycan; in protozoan parasites such as Giardia species, it's made of carbohydrates and proteins.

The part of the cytoplasm that does not contain organelles but which does contain other particulate matter, such as protein complexes.