Immunology Case study: Developed flu-like symptoms, severe diarrhoea and abdominal pain 4 days after attending a dinner party at which he had eaten a chicken casserole Homework Help

This should be answered in about 500 words, in a text format (i.e. not simply writing down the answers to the questions, but writing a proper explanation). The questions are there just to guide you. This will require some research on your part- I recommend textbooks such as Kuby or Roitt, and a swift search on the web- but be careful to use only high quality sites.
In marking I am looking for accuracy, clarity, and explanations of the symptoms in terms of molecular and/or cellular immunology.

Mr JD is 23-year-old man developed flu-like symptoms, severe diarrhoea and abdominal pain 4 days after attending a dinner party at which he had eaten a chicken casserole. Three other people who had attended the same party developed gastrointestinal symptoms. These symptoms settled within a few days. Stool cultures taken from all four individuals grew Campylobacter jejuni.
About 10 days after the onset of diarrhoea, he developed diffuse aching around his shoulders and buttocks and pins and needles in his hands and feet. Over the next week the sensory changes worsened and spread to involve his arms and legs. His limbs became progressively weaker and 8 days after the onset of neurological symptoms he could not hold a cup or stand unaided. He was admitted to hospital and found to have severe symmetrical distal limb weakness and ‘glove and stocking’ sensory loss to the elbows and knees.
Nerve conduction studies showed evidence of a mixed motor and sensory neuropathy (with apparent demyelination) and, after lumbar puncture, examination of his cerebrospinal fluid (CSF) showed a very high total protein level at 4g/l but without any increase in the number of cells in the CSF. High titres of IgM and IgG antibodies to Campylobacter jejuni were found in his peripheral blood. A diagnosis was made of the Guillain–Barré syndrome (acute inflammatory polyneuropathy) probably triggered by Campylobacter jejuni infection. He was treated with high-dose intravenous immunoglobulin but his condition deteriorated with respiratory muscle weakness and he required mechanical ventilation. His condition slowly improved and he was able to breathe spontaneously after 2 weeks. His strength and sensory symptoms slowly improved with vigorous physiotherapy but 1 year after the initial illness he still had significant weakness in his hands and feet.

1. Why would a bacterial infection lead to an acute idiopathic inflammatory polyneuropathy?
2. Antibodies to ganglioside GD1 were subsequently shown in the pretreatment serum sample- why would that be?
3. What is the point of giving high dose intravenous immunoglobulin?