Blood Leukocytes and Histology of Immunopathology
for Microbiology 542, Immunology Laboratory -- Eric Martz, Instructor -- 2000

  1. Identify and characterize six kinds of leukocytes in human blood smears.
  2. Observe a histologic section of a human lymph node, identifying key features.
  3. Observe a normal tissue and the same tissue containing immunopathology. Record your observations including your interpretation of the mechanism responsible for the immunopathology.
Organize all observations, notes, and sketches in your notebook.

I. Leukocytes in Blood Smears

Use your microscope to examine a human blood smear slide. Fill out the Checklist for Blood Leukocytes. Ask the TA's for help with this. Add a column for NK cells and fill it out.

To aid your identification, use the wall charts, and the demonstration microscopes which are preset to show one of each kind of leukocyte.

Because they are rare, it is unlikely that you will be able to find clear examples of either a basophil or an NK cell, so don't waste time on these. If you do think you have found either, show it to Eric!

II. Human Lymph Node

In your section of human lymph node, identify the following. Items 2 and 3 may not be included in your section, but where would you expect to find them in your section if they were present? Ask TA's for help! A textbook of histology will be available.

  1. Capsule.
  2. Subcapsular sinus.
  3. Afferent (incoming) lymphatic vessel.
  4. Efferent (outgoing) lymphatic vessel.
  5. Follicles with or without germinal centers.
  6. Cortical lymphocytes.
  7. Medulla.
  8. Macrophages ingesting black debris.
  9. Vessels containing erythrocytes (no nucleus, stain bluish).
  10. Arteries, veins, capillaries, endothelium.
  11. Fat cells, nerves, collagen, fibroblasts and connective tissue.
If there is something you cannot identify, ask a TA. What is the origin of the black debris in the macrophages?



III. Histology of Immunopathology

Each bench will be allocated one or two slides of immunopathology, along with sections of the corresponding normal tissue. Your goal is to describe the major differences between the normal and the pathologic specimens, and then to interpret them. If you complete the specimens at your bench, you are welcome to observe specimens from other benches once they are no longer needed at that bench.

Normal and pathologic tissues available are listed below. In one case, the pathology is cancer rather than immunopathology.

Interpretation. Immunopathology is usually associated with a massive influx of hematogenous leukocytes. If the major trigger is immune complexes involving IgG, the major infltrating cell type will be neutrophils (polymorphonuclear cells). This results primarily from complement fixation and the release of C3a and C5a. If the predominant trigger is recognition of antigen by T lymphocytes, the major infiltrating cell type will be lymphocytes and macrophages (mononuclear cells). This results from T-cell released cytokines, notably gamma-interferon, and is called "delayed hypersensitivity" or "cellular immunity".

Normal slides, as well as the pathology slides for brain and lung are from commercial sources (Ward's supply house). Thanks are due the following who kindly donated these slides of pathology: