Lecture 31: Lymphadenopathy & HIV infection Flashcards
Lymphocytes: what are the types and what are their roles?
B lymphocytes: Plamsa cells 1/2
- Synthesise antibody IgG, IgM, IgA etc
T cytotoxic lymphocytes: CD8 and T8 lymphocytes 1/4
- Kill cells displating non self peptides in MHC molecules; ie; kill virus producing or cancerous cells
T helper Lymphocytes: CD4 and T4 lymphocytes 1/4
- Secrete cytokines to regulate other cells of the immune system
- eg; macrophages in a granuloma, B or T lymphocytes, neutrophils
- Organising cells that without, the IS would not function!
Causes of Lymphadenopathy
- Proliferation of lymphocytes in response to a local infection
- Proliferation of malignant cells that have metastasised to the node by lymphatic spread
- Proliferation of malignant lymphocytes
- Inflammation within nodes resulting from killing of lymphocytes infected by a virus
What investigations would you do with those who have lymphadenopathy?
- Look for adjacent infection (eg; boils, cellulitis)
- Look for adjacent cancer (breast, lung, skin)
- Look at features of cells in lymph node
- Look for evidence of an infection that targets lymphoid cells
Via a Fine Needle Aspiration (FNA) of cells from within a lymph node and/or excision of a lymph node ((are malignant cells present??)
Types of Bacterial and viral pathogens that can infect lymphnodes?
Bacteria (apart from these two very uncommon)
- Staph. aureus : from splinter in finger
- Mycobacterium tuberculosis
Viral (COMMON)
- Epstein Barr Virus (EBV)
- Cytomegalovirus (CMV)
- Human Immunodeficiency (HIV)
EBV and CMV are part of the ________ family. Describe this?
Part of the herpes family
- DNA viruses
- acute infection (causes illness) followed by latent infection (asymptomatic) with reactivation for the rest of their life
- chronic infection (asymptomatic)
Similar to Herpes Simplex virus (HSV) that causes cold sores or the varicella zoster virus (VZV) that causes chicken pox/shingles
What illnesses do EBV and CMV cause?
EBV → Glandular Fever
CMV → Less severe GF-like illness
both common causes of illness with generalised lymphadenopathy
Epstein Barr Virus
Glandular Fever = infectious mononucleosis = kissing disease
Minor illness when child
Much more severe when acquired as an adult!
Virus transmitted in saliva, with an incubation period of 4-6wks
Illness for 1-2wks (usually)
Fever, sore throat, malaise, cervical adenopathy, fatigue
Recovery, but persistent salivary excretion of EBV (infects LNs in tonsils, then spreads to other LNs)
Ways to diagnose acute EBV infection?
- Lymphocytosis (>50% of WBCs)
- Atypical Lymphocytes (>10% of lymphocytes)
- Abnormal Liver Function Tests
Paul Bennell = Monospot test
detects “heterophile” antibodies, which bind to guinea pig, sheep, horse RBCs but NOT to EBV!!! that are produced in response to the virus as well as ABs against the virus itself
Specific EBV serology:
Detects antibodies that EBV, detects EBV antigens
Acute HIV Infection
- Epidemiologic risk for HIV infection (sex w men, or in high risk countries)
- Recent (3-6wk previously) exposure
- Glandular fever-like illness: occurs at the end-of incubation period when the body is beginning to generate a response!
- Presistent viraeia and virus in genital secretions
- Presence of anitbodies to HIV in blood
HIV evolved from?
A closely related virus in chimpanzees in the early 1900’s, when people hunting/killing chimpanzees in africa got exposed to the blood
Cause a variation of viruses in different species.
HIV structure and replication
- Enveloped virus so that there’s an outer layer derived from the hosts cytoplasmic membrane
-
Protein molecules made in infected cell stick out of lipid bilayer for attachment to Helper T cells (CD4)
- as this is the attachment point CD4 cells are the only ones affected
- Protein cylinder inside that contains the RNA virus
HIV pathogenesis
- 109 T helper lymphocytes produced each day from bone marrow!
- HIV infects T helper lymphocytes
- Infected cells produce 109 HIV per day
- Productively infected cells are killed by cytotoxic lymphocytes
Timeline of HIV
ELISA: Enzyme Linked Immunosorbent Assay
- Common test for infections
- ANtibody will stick to HIV antigen that has been put in the tube.
- Anti-human antibody will attach to antibody
- Add enzyme that will be cleaved is enzyme from AHA (induces a colour change)
- Can messure amount of AB by the amount of colour change
AIDS (acquired Immune Deficiency Syndrome)
What infections define aids????
- Kaposi Sarcoma: cancer of blood vessle
- TOxoplasma brain abscess: we all have virus but our IS can control
HIV Treatment
Range of drugs that block virus attachment, RNA to DNA, virus exiting etc.
If you take the combo of 3 drugs the level of HIV infection in the blood can drop to 0 and with continued use can remain that way for life and remain healthy.
This means the virus drops to undetectable levels in genital secretions also and the person is not infectious.
Now the people dying of AIDs and contracting diseases has greatly diminished
Vaccines for HIV?
Risk of transmission of HIV per UNPROTECTED sex
- Some exposed but uninfected people have immune responses but doesn’t provide protection so NO VACCINE
