Ageing and Immunity Flashcards
Which infections are more common in the elderly?
- Sepsis
- Pneumonia
- Asymptomatic bacteruria -> UTIs
- Influenza
- Herpes zoster -> post-herpetic neuralgia
What are key features of the innate immune system?
- Rapid responses
- Physical barriers - muscosal membranes + skin
- Unchanged w/ repeated exposure
- Phagocytosis main cellular process
What are key features of the adaptive immune system?
- Specific reactive response
- Memory for recurrent exposure
- Lymphocytes - T + B
- Speel + thymus important organs
Which cells are involved in innate immunity and which one of these is the main antigen-presenting cell?
- Mast cell
- Dendritic cell
- Macrophage
- Neutrophil
- Eosinophil
- Basophil
- Complement protein
- Natural killer cell
What is the role of the dendritic cell?
Dendritic cell performs some phagocytosis but presents new antigens to T cells - this is where adaptive immunity is initiated.
What happens to neutrophils during ageing?
- Less recruitment to site of infection
- Less phagocytosis
- Less signalling
- Less intracellular killing
What happens to dendritic cells during ageing?
- Less phagocytosis
- Less migration
- Reduced antigen capture + presentation
What happens to macrophages during ageing?
- Reduced recruitment to site of infection
- Causes more collateral damage (to healthy cells as well)
- Reduced phagocytosis + killing ability
What changes occur in B-cells in regards to ageing?
- More non-specific antibodies produced
- More antibodies against self-antigens (autoimmune)
- Lower affinity + diversity of antibodies
Immunosenescence refers to the gradual deterioration of the immune system brought on by natural age advancement. Describe T-cell immunosenescence
- Thymic involution
- Reduction in naive T cells
- Less of new T cells, but more of old T cells
- Inability to respond to novel antigens
- Less T helper support of B cell population
Many cells produce cytokines, both pro and anti-inflammatory. Ageing is accompanied by an increase in which type? What are examples?
Ageing accompanied by increased pro-inflammatory cytokines - mainly IL-6, TNF-alpha
What does increased background inflammation (inflammaging) do?
- Reduces response to specific infective stressors
- Exacerbates conditions w inflammatory aetiology
- > autoimmune disease
- > alzheimer’s
- > cardiovascular disease
Elderly patients often don’t come to hospital presenting with typical infectious symptoms, so what do they come in with?
- Delirium
- Lethargy
- Falls
- Anorexia
Can be caused by anything
What is difficult about diagnosing elderly patients coming into hospital?
- 50% present later due to blunted inflammatory response
- Cognitive impairment makes history more difficult
- Imaging + microbiology specimens are difficult to obtain
Multiple admissions mean increased drug resistant organisms, such as?
- MRSA
- ESBL
Which healthcare associated infections are more common in elderly patients?
- Catheter Associated UTI
- Hospital acquired pneumonia
- C. diff
Co-morbidity increases likelihood of organ specific septic complications, such as?
- Acute kidney injury
- Cardiac dysfunction + type 2 MI
What do we see in regards to vaccination in elderly people?
- Vaccine response is attenuated (reduced) by immune senescence
- Response rate 30-40% in over 65s, 80% in under 65s
What is the impact of influenza vaccination?
- Benefit to older people due to high incidence + mortality
- Reduction in mortality, morbidity + hospitalisation
What other vaccination is often co-administered with the influenza vaccine?
- Pneumococcal vaccination
- Moderate efficacy in older people
- Cost-effective due to low cost of co-administration with flu vaccine
There are slight increase in autoimmune disease in the elderly. Specifically which autoantibody is more frequent?
Increased rheumatoid factor -> RA!
What is the median age of cancer diagnosis?
- 70
- Cancer incidence increases with age
In which individuals is there an increased frequency of cancer?
- Immunosupressed individuals:
- HIV
- Solid organ transplants
- Long term immunosupression for autoimmune conditions
What is immunosurveillance?
- If a normal cell is faulty/abnormally functioning, it will kill itself by apoptosis
- Cancer is the upregulation of abnormal endogenous cells
- Precursor cells of cancer in whom apoptosis has not occurred should be destroyed by a healthy immune system
- So immunosurveillance is a important role of the immune system
How does immune senescence (T cells) contribute to an increased likelihood of cancer?
- Particularly T cells reduced identification of abnormal cells
- Decreased cytotoxic activity
- Allows tumour cells to escape immunosurveillance + subsequent destruction
