The aim of this study was to evaluate the levels of disaccharidase and dipeptidyl peptidase IV activities in rat jejunal enterocytes under the influence of long-term germ-free conditions. We found that the brush-border lactase and dipeptidyl peptidase IV activities were two to three times higher in 2-month-old germ-free rats in comparison with their conventional counterparts. The highest effect of germ-free condition was observed on lactase activity in 6-month-old and dipeptidyl peptidase IV in 2-month-old rats. No difference between germ-free and conventional rats in sucrase and glucoamylase activities was found in 2-month-old rats. The difference develops with increasing age, sucrase activity becoming significantly higher in 6- and 12-month-old rats and glucoamylase in 12-month-old germ-free rats.
An allogeneic reaction among brain cortex cells (mixed reaction) was demonstrated previously by H-2 alloantigen- induced uncoupling of oxidative metabolism (Kovářů Med. Biol. 58: 273, 1980). In the present study we have demonstrated that alloantigen already increased cell surface Na + ,K+-ATPase activity after 100 min when the enzyme activation was highest at Mg2+/ATP ratio 4: 1. The allogeneic cell reaction was accompanied by an elevation of membrane lipid fluidity and probably also by a thermotropic lipid phase transition which might influence the membrane lipid-dependent Na+,K+-ATPase activity, while Mg2+-ATPase remained unaffected. Furthermore, the effects of proteins and peptides released into the supernatant during the allogeneic reaction were analyzed in brain cortex cells. One of the isolated active peptide fractions, Fa (m.w. lower than 2.5 kD), was able to enhance Na+,K+-ATPase activity as well as to block K+-evoked O2 uptake by brain cortex cells. Thus the Fa fraction simulated primary allorecognition events. The data indicate that various brain cell surface domains were influenced by a regulatory peptide fraction of the cytokine type during the early phase of allogeneic reaction. Allorecognition among brain cortex cells is directed against functionally important metabolic reactions.
This study describes the effects of cytokine peptides released into the supernatant during an early allogeneic reaction (AR) of mouse spleen lymphocytes or brain cortex cells which differ in their major histocompatibility complex (MHC). The peptides were isolated by ultrafiltration, liquid chromatography and HPLC. We found that both peptides stimulated the cell surface Na+,K+-ATPase and Ca2+-ATPase activities of quiescent spleen lymphocytes in vitro and mimicked early allogeneic cell interactions. Both brain and spleen AR peptides inhibited Concanavalin A-stimulated spleen lymphocyte proliferation, whereas 3H-TdR incorporation into DNA of the E7 neuroblastoma cell Une was stimulated by these peptides. The peptide isolated from the supernatant of the allogeneic brain ceU reaction inhibited phagocytosis in phorbol myristate-stimulated LA5-9/8 mouse macrophage cell line. Immunosuppressive activity of spleen AR peptide is supported by inhibition of spontaneous E rosette formation by lymphocytes. The immunosuppressive effect of isolated peptide cytokines on lectin-activated lymphocytes was comparable with the serum thymic factor (FTS, Lenfant et al. 1983). These changes demonstrate the pleiotropic cytokine actions mediated by plasma membrane of immune system and brain cells.