Host-microbe immune response Flashcards
What is present in the skin that acts as an immunological barrier?
Keratinocytes secrete antimicrobial peptides such as defensins
Sebaceous/sweat glands secrete microbe-inhibiting substances (fatty acids)
Antigen-presenting cells - langerhans
What is present in the mucosa of the resp/GI/GU tract that acts as an immunological barrier?
Antimicrobial substances such as lysozyme
IgA
Gastric acid
What clinical problems in the skin can lead to infections?
Eczema,psoriasis, erythroderma
Tinea pedis
Ulcers
Pressure sores
What clinical problems in the lungs can lead to infection?
CF
Bronchiectasis
COPD
Poor swallow
What clinical problems in the GI tract can lead to infection?
Mucositis secondary to chemo
IBD
Bowel cancer
What clinical problems in the GU tract can lead to infection?
Impaired bladder emptying e.g. benign prostatic hyperplasia
Catheterisation
What are phagocytes?
Neutrophils (blood) and macrophages (tissue)
What infections can be seen deficiencies of phagocytes?
Strep Staph Coliforms Aspergillus Candida
What conditions can lead to deficiencies of phagocytes?
Haematological malignancy (acute leukaemia, myelodysplasia) Cytotoxic chemo
What is the action of CD4+ T lymphocytes?
Active phagocytes to kill microbes
What is the action of CD8+ T cells?
Destroy infection cells containing microbes or microbial proteins
What infections can be seen in deficiencies in T lymphocytes?
Viruses
Fungi
Mycobacteria
Parasites
What conditions can lead to deficiencies to T lymphocytes?
HIV infection (acquired deficiency in CD4+) Lymphoma Primary immunodeficiency syndromes (SCID)
What pathogens will B cells destroy?
Bacteria
Viruses
What conditions can lead to deficiencies in B cells?
Myeloma (paraproteinemia with immune paresis)
Primary immunodeficiency syndromes
Certain immune suppressants e.g. rituximab
Describe the pathological process of HIV?
HIV infects CD4+ T lymphocytes and produces a progressive decline in numbers of CD4+ lymphocytes resulting in deficiency in cell-mediated immunity
What conditions are HIV infected people susceptible to?
Invasive S.pneumoniae (bacteraemia/meningitis/empyema) irrespective of CD4 count
CD <350: TB, candidiasis
CD4<200: pneumocystis jirovecii, toxoplasma
CD4 <100: cryptococcus neoformans, CMV
What is hyposplenism and what can cause it?
Decreased spleen function
Splenectomy (trauma, ITP, lymphoma) or functional hyposplenism (sickle cell, cirrhosis, coeliac disease)
What conditions are those with hyposplenism more susceptible to?
Streptococcus pneumoniae
Haemophilus influenzae
Neisseria meningitidis (meningococcus)
How can the risk of infections in hyposplenism be reduced?
Vaccination before the splenectomy
Why are the elderly more susceptible to infections?
Phagocytes destroy bacteria/antigen more slowly
T cells respond more slowly
Less antibody is produced and it binds to antigen less well
Less complement produced
What conditions is immune suppression required in?
Inflammatory arthritis Vasculitis/ connective tissue diseases Glomerulonephritis IBD Interstitial lung disease ITP/ autoimmune haemolytic anaemia Transplants: solid organ or bone marrow Cancer: biologics used in breast/lung/liver cancer and melanoma
What are the effects of immune compression?
Blunted response to stimulus
Will not exhibit the same response to infections as “normal people”: absent fever, lack of inflammatory response (CRP/neutrophils), non-specifically unwell
What will immunosuppression with steroids make you susceptible to?
Fungal infections (candida, aspergillus)
