Lymphocytosis promoting factor (LPF) of Bordetella pertussis is a protein toxin which may have a role in the pathogenesis of pertussis. Since macrophages have an important role in the control of respiratory infections, the in vitro effects of LPF on macrophages from C3H/HeN and C3H/HeJ mice and on a murine macrophagelike cell line, RAW264, were examined. LPF inhibited random migration of resident peritoneal macrophages as well as the chemotaxis of peritoneal macrophages and the cell line. Fifty percent inhibition of chemotaxis occurred at 0.2 to 0.3 ng of LPF per ml for the macrophages and at 1 to 2 ng of LPF per ml for the cell line. When LPF was either heated at 80°C for 5 min or premixed with specific antibodies, it failed to inhibit migration. At 20 ng/ml, LPF inhibited chemotaxis by more than 80% and also decreased Fc-mediated phagocytosis by 25 to 35%. At this dose, LPF was not a chemoattractant for murine macrophages and did not reduce macrophage viability, adherence, or opsonized zymosan-stimulated superoxide release. When LPFtreated macrophages were added to tissue culture dishes and then examined microscopically after 4 h, the LPFtreated cells adhered but failed to spread and elongate as well as control macrophages. These data indicate that LPF specifically inhibits macrophage migration in vitro and suggest that a possible role for LPF in pathogenesis is to inhibit migration of macrophages to the site of B. pertussis infection.
Previous results from our laboratory demonstrated that purified lymphocytosis-promoting factor (LPF), a protein toxin from Bordetella pertussis, inhibited the migration of murine macrophages in vitro. The current study examined the in vivo effects of LPF on mononuclear phagocyte circulation and response to an inflammatory stimulus. Intravenous injection of mice with 200 ng of LPF produced a prolonged monocytosis which peaked with a fivefold increase on day 5 after injection. LPF (200 ng) also inhibited by more than 75% the increase in peritoneal inflammatory macrophages induced by intraperitoneal injection of thioglycolate broth, phytohemagglutinin, or paraffin oil. The inhibition was significant when thioglycolate was given 1 h or 2 or 4 days after LPF but not when thioglycolate was given 2 or 4 days before LPF. The LPF-induced monocytosis on day 5 after injections was not altered by the intraperitoneal injection of thioglycolate broth. The leukocytosis-promoting and macrophage-inhibiting properties of LPF were the same in N:NIH(S) and C3H/HeJ mice. Treatments of LPF that reduced the leukocytosis-promoting effect of LPF also reduced the ability of LPF to inhibit the macrophage response. LPF doses sufficient to induce leukocytosis (.25 ng) significantly inhibited the thioglycolate-induced increase in peritoneal macrophages. The results indicate that coincident with an LPF-induced monocytosis is a reduction in the number of mononuclear phagocytes at a site of inflammation. An in vivo inhibition of mononuclear phagocyte migration would explain both effects of LPF and is consistent with the in vitro inhibition of macrophage migration by LPF.
Two inclusions of the endoplasmic reticulum, tubuloreticular inclusion (TRI) and cylindrical confronting cisternae (CCC), are common to lymphocytes from individuals with AIDS and AIDS-related conditions. Both inclusions can be induced in vitro with alpha-interferon (IFN). IFN may also be elevated in both populations. Circulating lymphocytes containing TRI are seen prior to the appearance of serum IFN. CCC appear in circulating lymphocytes after TRI, and both regularly antedate the diagnosis of AIDS. As in systemic lupus erythematosus (SLE), it can be hypothesized that lymphocytes exposed locally to IFN acquire TRI and then appear in the peripheral blood to be followed subsequently by IFN. The data strongly suggest that the appearance of these markers may predict the progression to AIDS.
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