The major role of<unk>  is to trap particulate antigen from the circulation and present the antigen to the lymphocytes of the spleen. Experiments have shown that inert latex beads as well as live bacteria such as Escherichia coli and Listeria monocytogenes are trapped by the<unk> . However, only immunogenic substances, i.e. bacteria, are trafficked to the T and B cell zones of the white-pulp and are efficiently presented to elicit an immune response. Lymphocytes<unk>  lymphocytes are a type of B cell <unk>  B cell, abbreviated "MZ B cell") created there, capable of binding IgM-antigen complexes. They are notable for their ability to serve several different roles in the immune system.<unk>  B cells express polyreactive BCRs that bind to multiple microbial molecular patterns.<unk>  Macrophages Within the<unk>  there exists two types of macrophages that are unique to this area: the<unk>  macrophages and the<unk>  metallophilic macrophages. These two macrophage sub-types are characterized by the expression of SIGN-R1 on the<unk>  macrophages and CD169 (siglec-1, sialoadhesin) on the<unk>  metallophilic macrophages. In addition to the<unk>  B-cells that normally reside there, a number of other cell types that are present in the blood pass through the<unk>  e.g. lymphocytes and granulocytes. In addition, a large number of dendritic cells are thought to reside temporarily in the<unk>  before migrating into the white pulp following stimulation and antigen uptake, as well as a large number of lymphocytes remaining in the<unk>  for a period of time during the process of transmigration into the white pulp. It can be assumed that both these cells wills interact with the<unk>  macrophages. Recent studies have shown that the<unk>  macrophages possess both important innate functions, as well as being able to promote adaptive immune responses, so these macrophages can bridge the innate and adaptive immunity. The<unk>  macrophages have a variety of functions, one of which is the phagocytosis of blood-borne pathogens. Because of the anatomy of the<unk> , the blood within it slows down and therefore the pathogens present in the systemic circulation are phagocytosed by both<unk>  macrophages. There is limited data regarding the specific roles of these two macrophage subsets in the uptake and eradication of pathogens. However there is evidence and reports that show there is a specific involvement of the various pathogen receptors on the<unk>  macrophages in recognising and eliminating certain pathogens, especially encapsulated bacteria. For example, the C-type lectin SIGN-R1 receptor (present on the<unk>  macrophages), mediates the recognition of pneumococcal saccharides and is necessary for Streptococcus pneumoniae clearance. Furthermore, both types of<unk>  macrophages in the clearance and degradation of viruses e.g. cowpox virus and adenovirus serotype 5. Evidence has shown that the clearance of lymphocytic choriomeningitis virus by<unk>  macrophages is crucial to prevent the spreading of viral infections to peripheral organs.
Marginal zone
Blue zone
Inner nuclear layer
Watershed area 
Outer nuclear layer
Trigger zone
Episcleral layer
Sommer's sector