Clinical diagnosis
Case 130
【Progress】Blood culture revealed invasive group B streptococcal infection. Regrettably, despite intensive treatment and care, she passed away twenty five days later.
【Discussion】
Spleen compose of red pulp, white pulp and marginal area which separates between red pulp and white pulp. Each component has blood supply from splenic artery. The red pulp get much more blood supply than other two components. The red pulp is full of erythrocytes, platelets and macrophages. In case that bleeding occurs, the red pulp functions the release of erythrocytes, platelets and macrophages to compensate for blood loss and help to stop bleeding and reduce the inflammation, respectively. Macrophages in the red pulp phagocyte the elderly erythrocytes and platelets, recycling iron. White pulp has a similar structure as lymphatic channel and owns T cell zone and B cell zone which create IgA, IgM and IgG against blood-borne bacteria, viral and fungus infections. Marginal zone owns B cell and macrophage which play a role to trap to particulate antigen and phagocyte the bacteria from the circulation, respectively. Macrophages and B cells in the marginal zone play a role as gate-keepers and present antigen to the lymphocytes of the spleen. B cells functions to rapidly antibody response to both T cell-dependent and T cell-independent antigens (1).
Bacteria and viruses have the capsule irrespective of thin or thick to protect themselves and adhere to the surface. Polysaccharide encapsulated bacteria such as streptococcus can evade from phagocytosis by macrophages and from opsonization by neutrophils (2). To activate immune system for phagocytosis and opsonization, speedy antibody production to polysaccharide capsule by B cells which means T cell-independent, is required. There are two immune clearances clarified in the spleen to fight against polysaccharide encapsulated bacteria. One clearance which occurs 24 hours after streptococcal infection is that macrophages in the red pulp and marginal zone uptake the bacteria which resistant to phagocytosis because of the polysaccharide capsule, inducing the presence of the bacteria at the surface and then, mobile neutrophils with complement (C3) adhere and opsonize the bacteria. The neutrophils are mobilized from the red zone and the whole blood. B cells get the information of the capsule through macrophages and/or directly via contact to the capsule. The second clearance which occurs 24 to 72 hours after infection is that antibody to the polysaccharides produced by B cells adhere to the bacteria and then, mobilized neutrophils opsonize the bacteria or macrophages phagocyte the bacteria (3-5).
When splenectomy was conducted, the body loses the main place of the immune response, inducing the proliferation of the bacteria. The life risk of overwhelming post-splenectomy syndrome was 5 % and the mortality rate was 38 to 70% (6). In our case, she underwent splenectomy 15 months ago because of the advanced gastric cancer. Infectious colitis caused by group B streptococcus induced overwhelming post-splenectomy syndrome, unfortunately leading to pass away.
As prophylaxis treatment, vaccine of the polysaccharide capsule is preferred to conduct for patients treated with splenectomy (7). B cells primed by the vaccination are easily accessible on the surface of the pathogen, and secret antigen-specific antibodies. Phagocytic cells such as macrophages and neutrophils take up and digest pathogens. In our institute, vaccination to the polysaccharide capsule is scheduled to conduct for patients after splenectomy.
【Summary】
We present fifty four-year-old female who had an attack of overwhelming streptococcal infection after splenectomy 15 months ago because of advanced gastric cancer. Unfortunately she passed away twenty fives later, despite intensive care and treatment. The life risk of overwhelming post-splenectomy syndrome was 5% and the mortality rate was 38-70%. We should keep in mind that streptococcus has a polysaccharide capsule which can evade from phagocytosis and antibody production to the capsule by B cell is critical to eliminate the bacteria. There are two clearance system to eliminate the bacteria in the spleen; first clearance by phagocyte of macrophages and opsonization of neutrophils with C3: second clearance by production of antibody to polysaccharide capsule by B cells in the marginal zone and opsonization of the bacteria by mobile neutrophils from red zone and whole blood. Prophylaxis treatment of vaccination might reduce the incidence of overwhelming post-splenectomy syndrome.
【References】
1.Bronte V, et al. The spleen in local and systemic regulation of immunity. Immunity. 2013; 14; 39(5): 806–818.
2.Hyams C, et al. The Streptococcus pneumoniae Capsule Inhibits Complement Activity and Neutrophil Phagocytosis by Multiple Mechanisms. Infect Immun. 2010 Feb; 78(2): 704–715.
3.Cerutti A, et al. Marginal zone B cells: virtues of innatelike antibody-producing lymphocytes. Nat Rev Immunol. 2013 Feb; 13(2): 118–132.
4.Zouali M, et al. Marginal Zone B-Cells, a Gatekeeper of Innate Immunity. Front Immunol. 2011; 2: 63. . doi: 10.3389/fimmu.2011.00063
5.Scapini P, et al. Location in the spleen dictates the function of murine neutrophils. J Exp Med. 2017 May 1; 214(5): 1207–1209.
6.Sinwar, Prabhu (December 2014). "Overwhelming post splenectomy infection syndrome – Review study". 12 (12): 1314–1316. doi:10.1016/j.ijsu.2014.11.005.
7.Davidson RN, Wall RA (December 2001). "Prevention and management of infections in patients without a spleen". Clinical Microbiology and Infection. 7 (12): 657–60. doi:10.1046/j.1198-743x.2001.00355.x. PMID 11843905.
2018.11.21