Results
Lymphoid Organs of the Bluegill
To determine which organis of the bluegill contained lymphoid cells,
smears of blood or organ cell suspensions were stained with May-Grunwald-
Giemsa and examined for the cell types present. Of the tissues examined,
anterior kidney (head kidney or pronephros), spleen, thymus, and blood
were the major sources of lymphocytes. Very few lymphocytes we re found
in the liver, pancreas, gonads, or posterior kidneys. Gut-associated
lymphoid tissue or lymph nodes were not found.
Due to the close proximity of the thymus to the anterior kidney,
serial sections were made through the gill region of a small fish ('v 100 g,
< 1 yr old) and examined histologically. Figure 1 presents photomicro
graphs of representative sections through this region. The anterior kid
ney was seen to be a relatively diffuse organ containing an abundant number
of blood sinuses, had a relatively large number of red blood cells and
contained a heterogeneous mixture of white cells. In contrast, the
thymus contained fewer red blood cells, had few white cells other than
lymphocytes and contained Hassalls corpuscles. Therefore based upon
both the anatomic location and the histologic characteristics, it was
felt that these tissues were in fact anterior kidney and thymus.
Separation and Quantitation of Bluegill Lymphocytes
- Hypaque-Ficoll (p = 1.077) was used to siolate relatively pure
populations of lymphocytes (characterized morphologically) from the
18