Alveolar macrophages activated with concanavalin A and peripheral blood monocytes activated with lipopolysaccharide secrete type fi transforming growth factor (TGF-j6). There is minimal TGF-/3 secretion in unactivated monocytes, even though TGF-4 mRNA is expressed in these cells at a level similar to that in activated, lipopolysaccharidetreated cultures. U937 lymphoma cells, which have monocytic characteristics, also express mRNA for TGF-j3. Freshly isolated monocytes, both control and lipopolysaccharide-treated, secrete an acid-labile binding protein that inhibits TGF-,B action. We conclude the following: (i) that expression of TGF-1B mRNA is unrelated to monocyte activation, (ii) that secretion of TGF-fJ is induced by monocyte activation, and (iii) that cosecretion of TGF-13 and its monocyte/macrophage-derived binding protein may modulate growth factor action. In contrast, monocytic expression of other growth factor genes, such as the B chain of platelet-derived growth factor, is not constitutive and requires activation.Type , transforming growth factor (TGF-,l) (1-5), a peptide widely distributed in tissues of humans and other animals, has the unusual ability both to stimulate and inhibit the proliferation of cells in culture (6-10). Although the effect of TGF-,B on epithelial cells is consistently inhibitory (6, 7, 9), its role in mesenchymal cell proliferation is more complex (7,8,11). For example, TGF-,3 acts synergistically with epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) to stimulate mitosis of normal rat kidney (NRK) and smooth muscle cells cultured in soft agar yet antagonizes the effect of these mitogens by inhibiting mitosis of the same cells cultured as subconfluent monolayers (7,8,12,13 3 (8).A second cell type that acts as an important source of growth factors during tissue repair in vivo is the macrophage (18). This cell, which appears in healing wounds prior to the onset of a fibrotic response (19,20), is a paracrine source of growth factors. This paracrine role of macrophages during wound repair in vivo can be demonstrated in studies that show that fibrosis is suppressed when monocyte infiltration is blocked (21). Since activated macrophages are known to secrete PDGF (22-24), the present studies were designed to see if macrophages might also be a paracrine source of TGF-P. Both PDGF and TGF-,3 may have important roles in stimulating smooth muscle cell proliferation in atherogenesis (25) as well as in fibroblastic proliferation in connective tissue repair (13, 16). MATERIALS AND METHODSIsolation and Activation of Human Alveolar Macrophages. Alveolar macrophages were obtained by bronchoalveolar lavage of normal nonsmoking human volunteers; samples typically contained >90% alveolar macrophages, -8% lymphocytes, and <1% polymorphonuclear leukocytes (26). Alveolar macrophages were suspended (106 cells per ml) in serum-free medium [MCDB 104/Dulbecco Vogt phosphatebuffered saline (PBS), 1:1 (vol/vol); Irvine Scientific and GIBCO, respectively] supplemented with bov...

We have isolated eight rat lymphocyte-myeloma hybrid cell lines producing monoclonal antibodies that react with the 21,000-dalton transforming protein (p21) encoded by the v-ras gene of Harvey murine sarcoma virus (Ha-MuSV). These antibodies specifically immunoprecipitate both phosphorylated and non-phosphorylated forms of p21 from lysates of cells transformed by Ha-MuSV. All eight react with the products of closely related ras genes expressed in cells transformed by two additional sarcoma viruses (rat sarcoma virus and BALB sarcoma virus) or by a cellular Harvey-ras gene placed under the control of a viral promoter. Three of the antibodies also react strongly with the p21 encoded by the v-ras gene of Kirsten MuSV. These same three antibodies immunoprecipitate the predominant p21 species synthesized normally in a variety of rodent cell lines, including the p21 produced at high levels in 416B murine hemopoietic cells. This suggests that an endogenous gene closely related to Kirsten-ras is expressed in these cells. The monoclonal antibodies have been used to confirm two properties associated with p21: localization at the inner surface of the membrane of Ha-MuSV-transformed cells, assayed by immunofluorescence microscopy, and binding of guanine nucleotides.

The 3′ half of an endogenous mouse mammary tumor virus from a C3H mouse was cloned in the Charon 4A vector phage. A comparison of the proviral clone with previously published endogenous mouse mammary tumor virus restriction maps identified it as endogenous unit II (J. Cohen and H. Varmus, Nature [London] 278 :418-423, 1979), which is present in all inbred mouse strains derived from the original Bagg albino × DBA cross. The nucleotide sequence of the unit II long terminal redundancy (LTR) was determined and compared with the sequence previously determined for the exogenous C3H virus LTR (Donehower et al., J. Virol. 37 :226-238, 1981). Virtually all sequence differences between the two LTRs were base substitutions. The total amount of sequence divergence was 6.6%. The large open reading frame reported previously in the exogenous LTR was preserved in the endogenous LTR. In addition, the pattern of sequence divergence was highly nonrandom with respect to the putative amino acid codons of the two open reading frames. Most of the base substitutions in this region resulted in silent or conservative amino acid codon changes. The nonrandom divergence pattern indicates that selective forces are operating on this segment of DNA and argues that the putative protein is functional in the life cycle of mouse mammary tumor virus. Possible roles for the protein and its mode of expression are discussed.

Polyclonal antibodies have been raised to a series of synthetic peptides which correspond to essentially all regions of the transforming growth factor beta 1 (TGF-beta 1) molecule. All antisera were evaluated for their abilities to react with TGF-beta 1 and TGF-beta 2 in either the native or reduced form in enzyme-linked immunosorbent assays, Western blots, and immunoprecipitation assays. While all antisera demonstrated some ability to recognize TGF-beta 1 in these systems, there was limited cross-reactivity with TGF-beta 2, suggesting that substantial sequence or conformational differences exist between the two growth factors. On Western blots 5-10 ng of purified human platelet TGF-beta 1 could be detected when probed with affinity-purified peptide antisera generated against peptides corresponding to residues 48-77, 50-75, and 78-109 of the 112 amino acid TGF-beta 1 monomer. Antisera raised against peptides 50-75 and 78-109 were most effective in immunoprecipitating reduced and native 125I-TGF-beta 1, respectively. The antisera also were tested for their effectiveness in blocking the binding of 125I-TGF-beta 1 to its receptor. Anti-peptide 78-109 and anti-peptide 50-75 blocked 80% and 40% of the binding, respectively, while antibodies against amino-terminal peptides were without effect. These data suggest that the carboxyl-terminal region of TGF-beta 1 may play a significant role in the binding of the native ligand to its receptor.