Host-Microbe Interaction Flashcards
Initial immune protection is provided by what?
Physical barriers
What are the two main components of the immune system?
Innate (phagocytes / NK cells)
Acquired/adaptive (B cells / T cells)
Bacteria are controlled by what immune cells?
Phagocytes
B lymphocytes and antibodies
Complement
Fungi are controlled by what types of immune cells?
Phagocytes
T-lymphocytes
Eosinophils
Viruses are controlled by what types of immune cells?
T and B lymphocytes
Protozoa are controlled by what groups of immune cells?
T lymphocytes
Eosinophils
Worms are controlled by what 2 types of immune cell?
Mast cell
Eosinophils
What properties does the skin have which make it suitable as a physical barrier to infection?
Keratinocytes secrete antimicrobial peptides (defensins)
Sweat glands secrete microbe-inhibiting substances (e.g. fatty acids)
Antigen-presenting cells in skin
The mucous membranes of the Respiratory/GI/GU tracts contain which properties that make them suitable physical barriers to infection?
Antimicrobials e.g. lysozyme
IgA
Gastric acid
What disease processes can cause the skin to be an impaired physical barrier to infection?
- Eczema, psoriasis, erythroderma
- Tinea pedis / cracking of skin
- Ulcers / pressure sores
What lung diseases can impact the efficiency of the respiratory tract mucous as a physical barrier to infection?
- Cystic fibrosis / Bronchiectasis (impaired mucus clearance)
- COPD
- Poor swallow (neurological illness, e.g. stroke)
What diseases can affect the ability of the GI tract mucosa to be a suitable physical barrier to infection?
- Mucositis secondary to chemotherapy
- IBD
- Bowel cancer
What WBCs are the main types of phagocyte?
Neutrophils and macrophages
In what conditions would a patient be deficient in phagocytes?
- Haematological malignancy (e.g. acute leukaemia)
- Cytotoxic chemotherapy
Describe the difference between CD4 and CD8 T cells
CD4 activate phagocytes to kill pathogen
CD8 Directly kill pathogen
What diseases cause a deficiency in T cells?
HIV infection (acquired deficiency in CD4) Lymphoma Primary immunodeficiency syndromes (e.g. SCID)
What antibody is produced first from B cells, and what antibody is produced most abundantly?
IgM = first (but has weak affinity) IgG = most abundant (strong affinity)
Deficiencies of B cells occur in what diseases?
- Myeloma (plasma cell cancer)
- Primary immunodeficiency syndromes
- Certain immune suppressants (e.g. rituximab)
There is a high risk of strep. pneumoniae infection in patients with HIV, regardless of their CD4 count. TRUE/FALSE?
TRUE
In HIV, a CD4 count of <350 predisposes to what infections?
Mycobacterium tuberculosis TB
Candidiasis
In HIV, a CD4 count of <200 predisposes to what infections?
Pneumocystis jirovecii
Toxoplasma gondii
In HIV, a CD4 count of <100 predisposes to what infections?
Cryptococcus neoformans
Cytomegalovirus (CMV)
What can lead to hyposplenism?
Splenectomy
=> (trauma, ITP, lymphoma)
”Functional” hyposplenism
=> (sickle cell, cirrhosis, coeliac disease)
Patients with hyposplenism are particularly at risk of infection from what types of organisms?
ENCAPSULATED ORGANISMS
- Streptococcus pneumoniae (pneumococcus)
- Haemophilus influenzae type B (HiB)
- Neisseria meningitidis (meningococcus)
How can risk of encapsulated organism infection in hyposplenism be reduced?
Vaccinations (particularly before splenectomy if this is the case)
Elderly patients are more prone to infections. TRUE/FALSE?
TRUE
- Less able to distinguish self from non-self (autoimmune disorders common)
- Immune system reacts slower and produces less immune cells
What is the main aim of immunosuppressive drugs?
Reduce damage due to the immune response
In what ways do immunocompromised patients not respond to infection in the same way as normal patients?
- Fever may be absent
- Lack of inflammatory response (CRP / neutrophilia)
- Non-specifically unwell (illness not localised)
There is often a lower threshold for treatment in patients who are known to be immunocompromised. TRUE/FALSE?
TRUE
Steroids are particularly associated with what type of infections?
fungal infections (Candida, Aspergillus)
Anti-TNF therapies (infliximab/etanercept) are particularly associated with what types of infection?
Mycobacterium tuberculosis (TB)
Fungal infections (Aspergillus)
What infections are associated with purine analogue drugs?
Viral infections (Herpes Simplex and Varicella Zoster)
Pneumocystis jirovecii
In what patients is the risk of infection so high that we would prescribe prophylactic antibiotics?
Co-trimoxazole in patients with HIV
Antifungal (e.g. itraconazole) in bone marrow transplant recipient
What groups of patients are all eligible for their flu vaccine?
PREGNANT WOMEN Chronic heart/lung/kidney/liver disease Immunocompromise Diabetes Aged >65 years
What groups of patients qualify for a pneumococcal vaccine
HYPOSPLENISM Chronic heart/lung/kidney/liver disease Immunocompromise (including HIV infection) Diabetes Aged >65 years
The Haemophilus influenzae type B (HiB) / DTP/ MMR vaccine is now given to ALL children. TRUE/FALSE?
TRUE
What causes the “cytokine storm” of unregulated inflammation in SEPSIS which eventually causes organ dysfunction?
IL-1
TNFa
IL-17
Why does Lactate rise during SEPSIS?
Tissue hypoxia
=>Cells must respirate Anaerobically
=> lactic acid production
Lactate production in sepsis creates a metabolic acidosis with what complication?
Acidosis worsens cardiovascular stability
