In this study cell proliferation in Peyer’s Patches (PP) and the crypts of Lieberkuhn of the follicle-associated ileal epithelium was analyzed during the development of acute lethal graft-versus-host disease (GVHD) in adult rats. In addition, the effect of thymectomy on GVHD-induced lymphoproliferation was determined by analyzing the3H-thymidine labeling index in neonatally thymectomized-control and thymectomized-GVHD rats. A significant increase in the3H-thymidine-labeling index was found in interfollicular (days 2–7), dome (days 5–10), and follicular (days 5–12) regions of PP as well as in associated ileal crypts (days 5–12) of GVHD rats as compared with controls. Thymectomy altered the proliferative response in PP of GVHD rats in that incorporation of3H-thymidine by follicular and interfollicular cells was significantly lower than in sham-thymectomized GVHD controls during the later stages of the disease. The results suggest a possible role for host thymus-dependent cells in stimulation of or participation in cell proliferation within follicular and interfollicular areas of PP.

Lupus or normal controls' sera, depleted of anti-DNA antibody and of DNA, were tested for their capacity to suppress the binding of3H-DNA to DNA-binding cells. Sera from lupus patients with inactive disease were effective in suppressing the binding (P<0.01) and, in the presence of complement, were more efficient in suppression (P<0.001). The same sera were capable of suppressing the in vitro secretion of DNA antibodies but not polyclonal IgG by autologous cells. The suppressor factor in the inactive lupus serum was shown to reside in the F(ab)'2 fragments of IgG and has a specificity for the F(ab')2 fragments but not the Fc fragments of anti-DNA antibody. Sera from active lupus patients and human serum albumin were incapable of suppression. Normal sera from donors who had contact with lupus blood components were efficient in suppressing DNA-binding cells (P<0.01).

A single intraperitoneal injection of 1000 mg/kg body weight of a PCB mixture (Aroclor 1242) to adult male BALB/c mice caused not only a relative spleen enlargement, but also an absolute spleen lymphocyte depletion. However, there was an enrichment of spleen T cells necessary to cause a graft-versus-host reaction (GVHR) in (C3H × BALB/c) F1 neonates. The effect was present 6 days after PCB administration and was no longer present on days 12–13. These studies suggest a transient effect of acutely administered PCBs on splenic lymphocytes (B cells, null cells, some T cells) other than mature GVH inducing T cells. The effect may be either similar to or possibly indirectly mediated by corticosteroids.

A sequential analysis was made of various areas within the lymph nodes and spleen of newborn Brown Norway (BN) rats suffering from graftversus-host disease (GVHD) subsequent to an allogeneic injection of adult Lewis (L) lymph node cells (experimental). One micron thick autoradiographs were compared between such experimental and control littermates having received the same number of syngeneic adult BN cells. Both experimental and control animals received tritiated deoxythymidine (3HdT) one hour before killing. The autoradiographs revealed a 2.25 and 2.50 times higher thymidine labeling index of lymphocytes in the deep cortex of mesenteric lymph nodes and white pulp of the spleen, respectively, for experimental animals. The experimental effect occurred within one day. The majority of the labeled cells in experimental animals were large lymphoblasts with prominent nucleoli. The labeling index within these areas remained significantly higher than control values until day 8 in the spleen and through day 14 within the lymph nodes. However, differences in labeled cells present in high powered microscopic fields reached a peak on day 3 within compartments in experimental animals but fell significantly below control values by day 9 owing to a pronounced disappearance of both small and large lymphocytes from these areas, and a decreased intensity of individual cell labeling as the reaction progressed. In contradistinction the concentration of labeled cells present in high powered microscopic fields of lymph nodes’ medulla became 3.13 times controls by day 4. Most of these labeled cells contained a more basophilic cytoplasm than those found in the deep cortex and some were distinctly plasma cell precursors. In contrast to the deep cortex their concentration remained approximately three times control values until death.