Immune response against P815X2 mastocytoma growing in syngeneic DBA/2 mice. II. Morphometric assessment of immunoreactivity in the thymus and spleen related to lymphocyte subsets in peripheral blood.

To assess the significance of humoral immune mechanisms in host reactivity against the P815X2 mastocytoma grown in syngeneic DBA/2 mice, an approach was made to correlate immunomorphology of the thymus and spleen with the functional assays measuring cytotoxic (51Cr-release assay) and tumor cell membrane-bound antibodies (IF test) as well as phenotyping (with monoclonal antibodies Anti-Thy1.2, Anti-Lyt1, Anti-Lyt2, and Anti-I-Ad) the lymphocyte subsets in peripheral blood. The volume fractions (Vv) of the cortex (C), and medulla (M) of the thymus, as well as central (C-PALS) and peripheral periarteriolar lymphoid sheath (P-PALS) in the spleen were determined morphometrically. There was a steady increase of the C/M ratio from the control levels until day 8, not accompanied by any major fluctuations in the percentages of Thy1.2+ or I-Ad+ cells in C and M. In M, two significant peaks were found in Lyt1+/Lyt2+ cell ratio. In the spleen P-PALS, Thy1.2+/I-Ad+ cell ratio was subject to major early elevation, followed by a rapid and permanent decline to levels below the controls. Two high peaks of Lyt1+/Lyt2+ ratio were found in P-PALS, on day 10 and 16. In the C-PALS, a marked decline in Thy1.2+/I-Ad+ ratio was observed throughout the experiment. As determined by Vv, there was a marked early enlargement of P-PALS reaching the peak on day 4, and followed by a steady reduction reaching the control values on day 10. In peripheral blood, there was an initial increase of T-cells, leading to elevated Thy1.2+/I-Ad+ ratio and a subsequent elevation of Lyt1+/Lyt2+ ratio on day 8.(ABSTRACT TRUNCATED AT 250 WORDS)