Cell wall the cell membrane is the bacterial cell wall. Bacterial cell walls are made of peptidoglycan (also called murein), which is made from polysaccharide chains cross-linked by unusual peptides containing D-amino acids. Bacterial cell walls are different from the cell walls of plants and fungi which are made of cellulose and chitin, respectively. The cell wall of bacteria is also distinct from that of Archaea, which do not contain peptidoglycan. The cell wall is essential to the survival of many bacteria, although L-form bacteria can be produced in the laboratory that lack a cell wall. The antibiotic penicillin is able to
Natural killer cell NK cell activity. Most of our current knowledge is derived from investigations of mouse splenic and human peripheral blood NK cells. However, in recent years tissue-resident NK cell populations have been described. These specialized NK-cell subsets can play a role in organ homeostasis. For example, NK cells are enriched in the human liver with a specific phenotype and take part in the control of liver fibrosis. Cancer Terms Natural killer cell Natural killer cells, or NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system. The role NK cells play is analogous to that of cytotoxic