Fc-gamma receptor-ligand interactions enhance macrophage GSIB4-binding activity.

Activated macrophages have an increased ability to bind the lectin Griffonia simplicifolia-IB4 (GSIB4). Since macrophages readily use the Fc-receptor (FcR) during several immunologic and inflammatory processes, it is important to determine whether interactions with this moiety affect GSIB4-binding ability. Peritoneal macrophages cultured in vitro with Fc fragments of immunoglobulin G (IgG), whole IgG, or heat-aggregated IgG demonstrate an increase in this function. Conversely, treatment of macrophages with (Fab')2 fractions alone has no direct effect on this activity. Although the GSIB4-binding response is minimally expressed by normal macrophages, it is more markedly apparent on macrophages from LPS-treated animals. In both cases, however, pretrypsinization of the cells renders them refractory to IgG-mediated induction of the GSIB4-binding response. Moreover, macrophages cultured independently with IgG subclasses 1, 2a, or 3 demonstrate that the magnitude of their response to this signal is directly associated with the type of subclass used. Although each subclass enhanced the response, in this study interactions with IgG2a produced the best results. Overall, however, the greatest GSIB4-binding activity is generated when FcRs are crosslinked by aggregated IgG rather than simply bound by independent monomeric interactions at the FcRs. This suggests that the event of appropriately interacting with the FcRs amplifies the GSIB4-binding function. Such a mechanism could play a key role in coordinating the humoral, cell-mediated, and innate responses of the immune system.

Earthworms near leprosy patients' homes are negative for acid-fast bacilli by fite stain, providing no link between leprous armadillos (Dasypus novemcinctus) and human leprosy.

Enzootic leprosy has been recognized in armadillos in Louisiana since 1975. Contact with armadillos is being assessed as a risk factor for leprosy in three white women, lifelong residents of separate rural areas in northern Louisiana, which is a region without endemic leprosy. None has had any known exposure to human leprosy. Each was aware of armadillos (Dasypus novemcinctus) near or under her home for decades. In considering Possible environmental sources forMycobacterium leprae, we observed that all three had earthworm growth areas for fishing bait where soil was kept moist near their homes. The worms attracted armadillos. Since armadillos subsist on worms, grubs, and insects and because of the common feature of a "worm farm" near each home, we reasoned that earthworms might containM. leprae and be part of a cycle involving the armadillo and human beings. Worms from each home worm farm were studied. One site was sampled twice at patient 1's home, five sites were sampled once at patient 2's home, and three sites were sampled once at patient 3's home. A sample consisted of 3-4 worms, which were washed, purged, fixed live in 10% formalin, embedded in paraffin, sectioned, and stained with the Fite stain. Each was sagittally sectioned and examined by three independent observers. No acid-fast bacilli or other acid-fast structures were identified. We conclude that it is unlikely that earthworms are an environmental source or reservoir ofM. leprae.

Leprosy in six isolated residents of northern Louisiana. Time-clustered cases in an essentially nonendemic area.

Northern Louisiana has been essentially free of indigenous leprosy, and now it is not. Six new cases of leprosy have been diagnosed: three in 1986, the other three in 1985, 1983, and 1982, respectively. The patients had been lifelong residents of six scattered rural parishes. Leprosy had never been reported from five of them. No patient had had contact with human leprosy. The patients were white; four were women; the mean +/- SD age at onset was 60.3 +/- 16.4 years (age range, 31 to 80 years); and the mean +/- SD interval to diagnosis was 1.2 +/- 1.4 years. One patient had Hodgkin's disease at the age of 25 years and leprosy at the age of 31 years; another patient had cervical carcinoma. All rural northern Louisiana residents coexist with armadillos (Dasypus novemcinctus), some of which are infected with Mycobacterium leprae, the significance of which is unknown. Hypothetically, exposure to an unknown human case, reactivation of "asymptomatic" leprosy through immunosenescence or immunosuppression, or infection from an environmental source might have occurred. Because the patients lacked contact, travel, residence, and exposure risk factors, the origin of leprosy in the new indigenous cases is noteworthy and is not understood.

Environmental nonhuman sources of leprosy.

Leprosy has been considered to occur only after exposure to a human case. However, evidence has been accumulating that this conventional view is wrong and that an environmental nonhuman source is critical to some human infections with Mycobacterium leprae. Observations, some of which date back to the nineteenth century, support soil, vegetation, water, arthropods, and armadillos (Dasypus novemcinctus) as environmental sources of leprosy. Disparate clinical, epidemiologic, and microbiologic evidence has been critically reviewed in light of the fact that 50%-70% of sporadic cases of leprosy in well-studied populations occur in persons who have had no known contact with human leprosy. Historical data and current information alike substantiate the concept of nonhuman sources of the disease; recent observations with monoclonal antibody have shown that phenolic glycolipid-I antigen, which is unique to the M. leprae cell wall, is present in soil. In the absence of a technique for in vitro cultivation, indirect methods and the body of observations reviewed here persuasively favor but do not prove the existence of environmental nonhuman sources of M. leprae.