G. M. Hochwald

Interleukin 1 (IL-1) and tumor necrosis factor alpha are thought to contribute to the inflammatory response associated with autoimmune diseases. Transforming growth factor beta 1 (TGF-beta 1) counteracts many effects of these cytokines and has various immunosuppressive properties. In the present study, it is shown that microgram amounts of TGF-beta 1, injected daily for 1-2 weeks, protect against collagen-induced arthritis (CIA) and relapsing experimental allergic encephalomyelitis (REAE), the animal models for rheumatoid arthritis and multiple sclerosis, respectively. When administered during induction of the disease, TGF-beta 1 prevents CIA but only delays the onset of REAE by 2-3 days. However, when administered during a remission. TGF-beta 1 prevents the occurrence of relapses in REAE. The results suggest that TGF-beta 1 has powerful anti-inflammatory effects, mimicking in some respects the beneficial effects of immunosuppressive drugs in these experimental models of autoimmune disease, but without discernable adverse effects.

The site of formation of C-reactive protein (CxRP, CRP) has been studied with tissues from rabbits, monkeys, and human beings. Rabbits and monkeys were stimulated to produce the acute phase protein by injection of turpentine, croton oil, endotoxin, paratyphoid-typhoid vaccine, or pneumococci. C(14)-amino acid incorporation in vitro was demonstrated by means of autoradiography of immunoelectrophoretic patterns made with culture fluids. It was found that among many different tissues tested liver was the only tissue which incorporated C(14)-lysine and isoleucine into CxRP or CRP. Only livers taken 16 to 24 hr after various stimuli were active; livers from normal animals or from animals killed 3 to 9 hr after stimulation did not produce detectable amounts of CxRP. Inflamed muscle from the injection site did not show C(14)-amino acid incorporation into CxRP. Several human tissues were also cultured, and a few liver cultures found to contain labeled CRP. The formation of CxRP or CRP by the liver was always accompanied by enhanced C(14)-amino acid incorporation into other serum proteins, but the reverse was not always found.

Nerve growth factor (NGF) is a neurotrophic protein essential for the maintenance and growth of peripheral sympathetic neurons and basal forebrain cholinergic neurons. Recently, NGF has also been shown to have effects on cells of the immune system. In a search for extra neural sources of NGF, we detected NGF-specific mRNA in mouse T lymphocytes of both the CD4+ and CD8+ phenotypes with the use of an RNase protection assay, PCR, and DNA sequence analysis. In CD4+ cells, NGF was present in both Th1 and Th2 Ag-specific clones, but an increase of NGF-specific message was detected after antigenic stimulation only in Th2 clones. NGF mRNA was also detected in splenic B lymphocytes and in a cell line derived from a murine follicular center cell lymphoma. Translation into protein and secretion of NGF were demonstrated by Western blot analysis. The secreted NGF is in an active form capable of inducing differentiation of PC12 cells into sympathetic-like neurons. Furthermore, conditioned medium from clones or lines positive for NGF mRNA was capable of inducing p140 tyrosine kinase autophosphorylation in 3T3 fibroblasts transfected with cDNA encoding for the tyrosine kinase family NGF receptor. We conclude that lymphocytes synthesize and secrete NGF either as a para-autocrine factor acting on the immune system itself, or as a factor for the maintenance of peripheral neurons.

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease in which peripheral lymphoid cells are activated by immunization with myelin proteins and become effector cells that traverse the central nervous system (CNS) capillaries and initiate inflammatory demyelinating lesions. The administration of transforming growth factor-beta (TGF-beta) has been shown previously to decrease the incidence and severity of EAE. In our studies we have determined: 1) the effects of TGF-beta injected at different intervals after the EAE-inducing immunization; 2) the effect of TGF-beta on the development of sensitized T cells, as assayed by the proliferative responses of T cells from lymph nodes and peripheral blood; 3) the extent of lymphoid cell infiltration in CNS of TGF-beta-treated and control mice; and 4) the role of endogenous TGF-beta and TNF in determining the severity of both acute and relapsing EAE. The onset of acute-EAE in SJL mice, induced by immunization with spinal cord homogenate in CFA and pertussigen, is on days 10 to 15. Although daily i.p. injections of 0.2 to 2 micrograms TGF-beta 1 or TGF-beta 2 on days 5 to 9 after immunization are highly protective, injections on days 1 to 5 or 9 to 13 are not. Moreover, anti-TGF-beta accelerates and aggrevates EAE when given on days 5 and 9, but not on day 12. Anti-TNF, injected on days 5 and 9, provides a comparable degree of protection as does TGF-beta. Similarly, in relapsing EAE, anti-TGF-beta increases, whereas anti-TNF decreases the incidence and severity of relapses. TGF-beta treatment on days 5 to 9 does not influence the appearance of sensitized cells in peripheral blood and lymph nodes, but does prevent the accumulation of T cells in brain and spinal cord, as assayed on days 15 to 20. It is concluded that the protective effect of TGF-beta is exerted at the level of the target organ, CNS and/or its vascular endothelium, rather than through a direct effect on lymphoid cells, and that there is a small window of 4 days in which TGF-beta exerts its protective effect.

The development of a new method for the determination of the sites of serum protein formation has been described. The method involves the incorporation of C(14)-labeled amino acids by tissues cultured in vitro, and subsequent autoradiography of immunoelectrophoretic patterns prepared from a mixture of culture fluids and carrier serum with an antiserum against the carrier serum. This technique has been used to demonstrate formation of gamma-globulin, of beta(2)-macroglobulin, and of a component of C'(3) by mouse spleen tissue, and of various other serum proteins by liver tissue. The specificity and sensitivity of this method have been discussed, and some of its advantages and pitfalls were mentioned. In addition, a rabbit antimouse serum was prepared, and the immunoelectrophoretic patterns obtained with mouse serum were compared with those described in the literature.