PSG is an immune complex-mediated disease caused by antibodies produced against streptococcal antigens like streptococcal pyrogenic exotoxin B and nephritis-associated streptococcal plasmin receptor. These antigens activate the complement cascade and induce antibody responses, causing inflammation of the glomeruli. High blood pressure can result from PSG due to decreased kidney function impairing sodium handling. The renin-angiotensin-aldosterone system and sympathetic nervous system activate to reduce renal blood flow and increase sodium absorption in response to the reduced kidney function and blood pressure changes caused by PSG.

1. Paediatric case study
Describe the immune response that leads to PSG.
PSG is an immune complex-mediated disease. Several processes may participate in the
pathogenesis of renal damage.The two antigens isolated from nephritogenic streptococci a
cationic cysteine protease streptococcal pyrogenic exotoxin B and nephritis-associated
streptococcal plasmin receptor, which is a plasmin-binding protein with glyceraldehyde
phosphate dehydrogenase (also known as presorbing antigen or PA-Ag) has role in causing
disease. These antigens have an affinity for glomeruli and play role in inducing specific, long-
lasting antibody responses in patients with APSGN. Antibodies to exotoxin B and PA-Ag are
raised in the majority of patients with APSGN. Intravenous injections of PA-Ag results PSG in
animals. Antibodies to PA-Ag are found in patients with APSGN but absent in those with
uncomplicated streptococcal infection. PA-Ag is also activates the alternate pathway of the
complement cascade in persons with APSGN. Antibodies are also produced in addition to
streptococcal antigens are the rheumatoid factor, cryoglobulins, and antineutrophil cytoplasmic
serum antibodies.
http://jasn.asnjournals.org/content/23/3/381.full.pdf+html
http://emedicine.medscape.com/article/980685-clinical
Explain why blood pressure of tom increased as a consequence of this infection?
High blood pressure can harm your kidneys and weaken their ability to function normally.
Glomerulonephritis can also leads to high blood pressure because it decreases kidney function
and may affect how your kidneys handle sodium. The strep bacterial infection results the tiny
blood vessels in the filtering units of the kidneys (glomeruli) to become inflamed. This results in
the kidneys less able to filter the urine as it normally filters.
http://www.mayoclinic.org/diseases-conditions/glomerulonephritis/basics/causes/con-20024691
https://medlineplus.gov/ency/article/000503.htm
Describe the expected response of the renin-angiotensin system, to this change in blood
pressure, within the context of PSG.

2. Reduction in the flow of renal blood occurs by activation of the renin-angiotensin-aldosterone
system (RAAS) and sympathetic nervous system (SNS), causing increase in sodium absorption
of kidney tubular system. The reduced renal blood flow causes the proper functioning of kidney
too.
https://www.ncbi.nlm.nih.gov/pubmed/6996879
http://europepmc.org/abstract/med/6996879
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4067259/