Immunological and Genetic Evidence for a Crucial Role of IL-10 in Cutaneous Lesions in Humans Infected with Leishmania braziliensis

Leishmania major is a parasite that is known for being the cause of cutaneous disease that can vary from mild skin ulcers to severe mucocutaneous disfiguration in mice. The severity of the disease depends on several factors, one being IFN-γ cytokines. IFN-γ cytokines are important in adaptive immunity against viral and intracellular bacterial infections. IFN-γ cytokines are produced as part of the innate immune response and directly inhibit viral replication. The cytokine, IL-10, is capable of inhibiting IFN-γ cytokines and are found often in cutaneous lesions caused by L. major. Nonhealing cutaneous lesions in mice infected with L. major have been found to be associated with low levels of IFN-γ and high levels of IL-10. Studies on leishmaniasis have been done frequently on mice, but few have been performed on cutaneous leishmaniasis in human patients and with different Leishmania species. Because of this, it is still unclear what the mechanisms are that contribute to some patients being resistant to this disease compared to patients who develop cutaneous lesions. In this study, Salhi et al. (2008) investigated the cytokines that play a role in Leishmania infections in human patients using Leishmania braziliensis.

The study was performed in a population living in two villages and farms located at the edge of a forest in Bahia. This region was chosen because it is endemic for cutaneous leishmaniasis caused by L. braziliensis. Patients were mainly farmers and were chosen if they were diagnosed with cutaneous leishmaniasis and responded to Glucantime treatments. Blood samples were taken from the 140 test subjects and the peripheral blood mononuclear cells (PBMCs) were isolated by centrifugation before the cytokine levels were measured (Salhi et al. 2008)

The results suggest cytokines play a key role in cutaneous leishmaniasis. In patients diagnosed with cutaneous leishmaniasis from Leishmania braziliensis, IFN-γ levels were very low while IL-10 levels were much higher when they had larger, slower healing lesions. This is an important study because if more studies are conducted on IL-10 and IFN-γ cytokines, a more efficient cure for cutaneous leishmaniasis could result from this. Using this same experiment for other species of Leishmania could give us a better insight as to how to prevent these lesions from forming.

 

            This article relates to the study by Samuelson et al. (1991) “A Mouse Model of Leishmania braziliensis braziliensis Infection Produced by Coinjection with Sand Sly Saliva” because Samuelson et al. (1991) studied how L. braziliensis is transmitted to humans while Salhi et al. (2008) studied the cutaneous lesions that occur from L. braziliensis. Both studies focus on the effects of getting cutaneous leishmaniasis and are useful in understanding how cases of cutaneous leishmaniasis can vary in different patients.

Citation

A. Salhi, V. Rodrigues, F. Santoro, H. Dessein, A. Romano, L. Roberto Castellano, M. Sertorio, S. Rafati, C. Chevillard, A. Prata, A. Alcais, L. Argiro, A. Dessein, 2008, Immunological and Genetic Evidence for a Crucial Role of IL-10 in Cutaneous Lesions in Humans Infected with Leishmania braziliensis, Journal of Immunology, 180: 6139-6148

-Kaitlin Smith