Unit 2: Cytology and immunopathology
Histotechnology-II & Cytology notes · PTU syllabus (BMLS605-18)
On this page
Unit summary
Cytology diagnoses disease from cells, and immunopathology studies the immune system in disease. This unit covers fine needle aspiration and fluid cytology, the cytotechnologist's role, exfoliative cytology and the Papanicolaou technique, autoimmune disorders, HLA typing, T and B cells, ANA, ANCA and thyroid antibodies, cancer immunology and tissue typing for kidney transplants.
After this unit you can
- Describe FNAC and fluid cytology and the cytotechnologist's role
- Perform Pap staining and report cervical smears
- Explain autoimmune disorders and autoantibody tests
- Explain HLA typing, cancer immunology and transplant tissue typing
PTU syllabus topics
- Aspiration cytology principles and the cytotechnologist's role in FNAC and fluid cytology
- exfoliative cytology and the Papanicolaou technique for cervical smears
- autoimmune disorders
- HLA typing
- T and B cells
- ANA/ANCA/TMA
- cancer immunology
- tissue typing for kidney transplant
Sample
Cells aspirated with a fine needle
Cells shed or scraped from a surface
Sites
Lumps: thyroid, breast, lymph node
Cervix (Pap smear), sputum, urine
Main stains
Giemsa, Pap, H&E
Papanicolaou
Topic 1
Aspiration cytology and fluid cytology
- Fine needle aspiration cytology (FNAC): cells aspirated from a lump with a 22–25 gauge needle and syringe — thyroid, breast, lymph nodes, salivary glands; image-guided for deep organs. Rapid, cheap, minimally invasive; cannot show architecture fully.
- 1
Clean the site; fix the lump between fingers
- 2
Insert the needle; apply suction; move in several directions
- 3
Release suction before withdrawing
- 4
Expel material onto slides; spread gently
- 5
Air-dry some (Giemsa or MGG) and fix others wet in 95% alcohol (Pap, H&E)
- 6
Rinse the needle for cell block or flow cytometry
- Fluid cytology: pleural, peritoneal, CSF, urine — centrifuge (or cytospin), smear the sediment, make a cell block for immunostaining; look for malignant cells.
- Cytotechnologist's role: assist aspiration, ensure adequate and well-prepared smears, stain, screen slides and mark abnormal cells for the cytopathologist, maintain quality control (re-screening).
Topic 2
Exfoliative cytology and the Papanicolaou technique
- Exfoliative cytology: study of cells shed naturally or scraped from surfaces — cervix, sputum, urine, oral cavity.
- 1Fix smear immediately in 95% ethanol (wet fixation)
- 2Hydrate; stain nuclei with Harris's haematoxylin; differentiate and blue
- 3Dehydrate; OG-6 (orange G) for keratin
- 4EA-50 or EA-36 (eosin azure — eosin, light green, Bismarck brown) for cytoplasm
- 5Dehydrate, clear, mount
- Results: nuclei blue–black; superficial cells pink; intermediate and parabasal cells blue–green; keratinised cells orange.
- Cervical smear collection: Ayre's spatula and endocervical brush, or liquid-based cytology (LBC).
NILM
Negative for intraepithelial lesion or malignancy
Normal or reactive
ASC-US / ASC-H
Atypical squamous cells
Uncertain; HPV testing or colposcopy
LSIL
Low-grade squamous intraepithelial lesion
CIN 1, HPV effect (koilocytes)
HSIL
High-grade lesion
CIN 2–3
Squamous cell carcinoma
Invasive cancer
Treatment
Topic 3
Autoimmune disorders and autoantibodies
- Autoimmunity: loss of tolerance so the immune system attacks self antigens — organ-specific (Hashimoto's thyroiditis, type 1 diabetes, Graves') or systemic (SLE, rheumatoid arthritis).
ANA (antinuclear antibodies)
Indirect immunofluorescence on HEp-2 cells; patterns (homogeneous, speckled, nucleolar, centromere)
Screening for SLE (over 95% positive), other connective tissue diseases
Anti-dsDNA
ELISA, Crithidia IF
Specific for SLE
ANCA
IF on neutrophils: c-ANCA (PR3) and p-ANCA (MPO)
Granulomatosis with polyangiitis (c-ANCA); microscopic polyangiitis (p-ANCA)
Thyroid antibodies (TMA, anti-TPO, anti-thyroglobulin)
ELISA, agglutination
Hashimoto's thyroiditis, Graves' disease
Rheumatoid factor and anti-CCP
Latex, ELISA
Rheumatoid arthritis (anti-CCP more specific)
Topic 4
T and B cells
Maturation
Thymus
Bone marrow
Markers
CD3; CD4 helper, CD8 cytotoxic
CD19, CD20; surface immunoglobulin
Function
Cell-mediated immunity; help B cells
Antibody production (plasma cells)
Counting
Flow cytometry (CD4 count in HIV)
Flow cytometry
Topic 5
HLA typing
- Human leucocyte antigens (MHC) on chromosome 6: class I (HLA-A, B, C — on all nucleated cells) and class II (HLA-DR, DQ, DP — on antigen-presenting cells). Highly polymorphic.
- Serological
- Complement-dependent lymphocytotoxicity with typing sera
- Molecular
- PCR-SSP, SSO, sequencing — now standard
- Uses
- Organ and stem cell transplant matching, disease associations (HLA-B27 in ankylosing spondylitis), paternity and forensic testing
Topic 6
Cancer immunology
- Tumour antigens: tumour-specific and tumour-associated antigens. Tumour markers in blood: AFP (liver cancer, germ cell tumours), CEA (colorectal), PSA (prostate), CA-125 (ovary), CA 19-9 (pancreas), β-hCG (choriocarcinoma).
- Immune surveillance: NK cells and cytotoxic T cells kill tumour cells; tumours escape by reducing antigen expression and immune checkpoints (PD-1/PD-L1). Immunohistochemistry identifies tumour type (cytokeratin, CD45, HER2, ER and PR); immunotherapy includes monoclonal antibodies and checkpoint inhibitors.
Topic 7
Tissue typing for kidney transplant
- 1ABO compatibility between donor and recipient
- 2HLA typing of donor and recipient (HLA-A, B, DR matching)
- 3Screen recipient for HLA antibodies (panel reactive antibodies)
- 4Cross-match: complement-dependent cytotoxicity or flow cytometry cross-match — recipient serum with donor lymphocytes
- 5Positive cross-match (preformed donor-specific antibodies) contraindicates transplant — risk of hyperacute rejection
- Rejection types: hyperacute (minutes — preformed antibodies), acute (weeks to months — T cells), chronic (months to years).
Key terms
- FNAC
- Fine needle aspiration cytology
- Papanicolaou stain
- Polychrome stain for cytology smears
- Bethesda system
- Standard reporting system for cervical cytology
- ANA
- Antinuclear antibodies, screening test for autoimmune disease
- HLA
- Human leucocyte antigens determining tissue compatibility
Quick revision
- FNAC technique; fluid cytology and cell blocks; cytotechnologist's role.
- Exfoliative cytology; Pap stain steps and colours; Bethesda categories.
- Autoimmunity; ANA, anti-dsDNA, ANCA, thyroid antibodies, RF and anti-CCP.
- T vs B cells and markers; HLA classes and typing methods.
- Tumour markers; immune escape; IHC; transplant cross-match and rejection types.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Give two advantages of FNAC.
- Q2.How are Pap smears fixed?
- Q3.What does LSIL correspond to histologically?
- Q4.Which test is most specific for SLE?
- Q5.What is c-ANCA associated with?
- Q6.What does a positive transplant cross-match indicate?
Long-answer questions
- Q1.Describe FNAC and fluid cytology.
- Q2.Describe the Papanicolaou stain and the Bethesda system.
- Q3.Describe autoimmune disorders and autoantibody tests.
- Q4.Describe HLA typing and tissue typing for kidney transplantation.
Stuck on this unit?
Message SBS on WhatsApp for help with Histotechnology-II & Cytology, or to ask about studying B.Sc MLS at Synetic.