The parasitized RBCs are entrapped in the spleen and a marked immunological response occurs. The spleen subsequently becomes very congested, soft and starts to increase in size.This occurs more commonly in non-immune individuals and can lead ,in some instances, to spontaneous rupture of the spleen.In endemic areas of malaria, sometimes, the spleen enlarges and causes a syndrome named tropical splenomegaly syndrome and recently given the name of hyperactive malaria splenomegaly.The cause of this syndrome is postulated to be due to an abnormal immunologic response..
The greatest defense in the human body against Malaria is the spleen . In P. falciparum malaria , the mechanism of complications postulated due to 1) sequestration hypothesis & 2) cytokine hypothesis . The sequestration hypothesis suggests that sequestration takes place in the blood vessels for the organism to multiply & to evade the spleen ! It is the cytokines which destroy the malaria parasite along with the infected RBCs . It is the cytokines which is responsible for the complications of Falciparum Malaria . The reason for the splenomegaly is due to the destruction of of the infected RBCs & therefore the spleen plays an important role in the defence against malaria . In serosurveys for malaria , the spleen rate in children is considered a valuable epidemiological tool .
Thank Singh for this information and as you mentioned the spleen rate or index is used in endemic malaria regions to rate the enemicity of malaria,The spleen is the organ of mystery in the body as stated long ago and I am sure a lot of information will come forward with in this era of modern technology and advanced investigational tools.
I agree with Vasila and of course in addition the parasitized cells are trapped in the spleen and we all know these pitting and sculling functions of the spleen.
The splenic sinusoids become enlarged due to both hyperplasia and hypertrophy of the specialized splenic macrophages called Kupffer cells. These findings relate to activation of the spleen's reticuloendothelial system. Kupffer cell activation is also seen the hepatic sinusoids and can cause hepatomegaly.
An article I will attach is from Africa and describes the events with additional pathophysiological information:
Although the exact mechanism is uncertain, evidence suggests that exposure to malaria elicits exaggerated stimulation of polyclonal B lymphocytes, leading to excessive and partially uncontrolled production of immunoglobulin M (IgM) as the initiating event. IgM is polyclonal and is not specific for any particular malarial species. Tcell infiltration of the hepatic and splenic sinusoids accompanies this process. Serum cryoglobulin and autoantibody levels increase, as does the presence of high molecular weight immune complexes. The result is anemia, deposition of large immune complexes in Kupffer cells in the liver and spleen, reticuloendothelial cell hyperplasia, and hepatosplenomegaly. 2, 5, 6 ---Tesfamariam
In essence, the cellular changes within the spleen (and liver, etc) are responses to inflammation.
I had the privilege of working in hematopathology with Henry Rappaport at the U of Chicago. I was looking for his monograph on the hematopoietic system to scan a photo of the Kupffer cell hyperplasia and hypertrophy but could not find the book.
Ahmed Mohamedani is absolutely right. The enlargement is mainly due to trapping of parasitized rbcs. To declare the malaria endemicity levels, spleen index is used. Since, spleen is one of the components of immune system, other immune reactions in malaria infections will also contribute to the enlargement. lalitha kabilan
Spleen enlargement/Slenomegaly is a landmark feature of the human body which is fighting with malarial parasite. In fact, spleen size has been used as a tool to determine the intensity of malaria transmission in some endemic regions.
The spleen is a complex organ that is perfectly adapted to selectively filtering and destroying senescent red blood cells (RBCs), infectious microorganisms and
Plasmodium -parasitized RBCs. Infection by malaria is the most common
cause of spleen rupture and splenomegaly. Extensive remodelling of the human spleen in malaria infections is characterised by white pulp expansion and a diffuse hypercellularity in the splenic red pulp.The splenic sinusoids get enlarged owing to both hightened cell division (hyperplasia) and excessive growth (hypertrophy) of the specialized splenic macrophages (Kupffer cells).
Spleen is the main organ that generates the immune response to the malaria parasite and controls the removal of the infected red blood cells, as a result of which reticuloendothelial system is activated that causes enlargement of the spleen.
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