Cytotoxic cell involvement in human cutaneous leishmaniasis: assessments in active disease, under therapy and after clinical cure.

Cutaneous leishmaniasis (CL) is an important public health issue worldwide. The control of Leishmania infection depends on cellular immune mechanisms, and the inflammatory response may contribute to pathogenesis. A beneficial role of CD8(+) T lymphocytes has been proposed; nevertheless, other studies suggest a cytotoxic role of CD8(+) T lymphocytes involved in tissue damage, showing controversial role of these cells. The goal of the current study was to understand the immunopathology of CL and determine the profile of cytotoxic cells--such as CD4(+) T, natural killer and natural killer T cells--that might be involved in triggering immunological mechanisms, and may lead to cure or disease progression. The frequencies of cytotoxic cell populations in peripheral blood, obtained from patients with active disease, during treatment and after clinical healing, were assessed by flow cytometry. Cytotoxicity could not be related to a deleterious role in Leishmania braziliensis infection, as patients with active CL showed similar percentages of degranulation to healthy individuals (HI). Cured patients exhibited a lower percentage of degranulating cells, which may be due to a downregulation of the immune response. The understanding of the immunopathological mechanisms involved in CL and the commitment of cytotoxic cells enables improvements in therapeutic strategies.

Multifunctional CD4⁺ T cells in patients with American cutaneous leishmaniasis.

Leishmaniasis is a group of important parasitic diseases affecting millions worldwide. To understand more clearly the quality of T helper type 1 (Th1) response stimulated after Leishmania infection, we applied a multiparametric flow cytometry protocol to evaluate multifunctional T cells induced by crude antigen extracts obtained from promastigotes of Leishmania braziliensis (LbAg) and Leishmania amazonensis (LaAg) in peripheral blood mononuclear cells from healed cutaneous leishmaniasis patients. Although no significant difference was detected in the percentage of total interferon (IFN)-γ-producing CD4(+) T cells induced by both antigens, multiparametric flow cytometry analysis revealed clear differences in the quality of Th1 responses. LbAg induced an important proportion of multifunctional CD4(+) T cells (28% of the total Th1 response evaluated), whereas LaAg induced predominantly single-positive cells (68%), and 57% of those were IFN-γ single-positives. Multifunctional CD4(+) T cells showed the highest mean fluorescence intensity (MFI) for the three Th1 cytokines assessed and MFIs for IFN-γ and interleukin-2 from those cells stimulated with LbAg were significantly higher than those obtained after LaAg stimulation. These major differences observed in the generation of multifunctional CD4(+) T cells suggest that the quality of the Th1 response induced by L. amazonensis antigens can be involved in the mechanisms responsible for the high susceptibility observed in L. amazonensis-infected individuals. Ultimately, our results call attention to the importance of studying a Th1 response regarding its quality, not just its magnitude, and indicate that this kind of evaluation might help understanding of the complex and diverse immunopathogenesis of American tegumentary leishmaniasis.

Imunidade celular e humoral na hanseníase bordeline tuberculoid (BT) / Humoral and cellular immunity in bordeline tuberculoid (BT) leprosy

Foram estudados 20 pacientes com diagnóstico de hanseníase bordeline tuberculoid (BT), classificados segundo os critérios de Ridley & Jopling, bem como dois pacientes com forma Tuberculoid tuberculoid (TT), todos com baciloscopia negativa, exceto um, que apresentou índice baciloscópico 1+. Todos os pacientes foram avaliados quanto a sua capacidade de resposta imune humoral ao DBSA (antígeno sintético semelhante ao glicolipídeo fenólico I, específico do M, leprae) e 18 pacientes foram submetidos a testes de avaliaçåo da resposta imunocelular in vivo (teste Mitsuda) e in vitro (linfoproliferaçåo e produçåo de interferon-gama) frente ao Mycobacterium leprae. Observamos que 90 por cento dos pacientess apresentaram resultados negativos quanto à pesquisa de IgM anti-DBSA pelo método imunoenzimático ELISA (densidade óptica , 0,27), o que demonstra ser este teste inadequado para a detecçåo de pacientes paucibacilares. Quanto aos testes de imunidade celular, oito pacientes (44,4 por cento) apresentaram teste de Mitsuda positivo (>= 5mm), sendo os demais considerados negativos. Cerca de 89 por cento dos pacientes tiveram teste de Mitsuda maior ou igual a 3mm. Doze pacientes (66,7 por cento) tiveram resposta linfoproliferativa positiva (índice estimulatório >= 3,0) para o M. leprae. Vinte e dois por cento dos pacientes apresentaram níveis de interferon-gama acima do limite de positividade (40 U/ml). Houve 66,7 por cento de correlaçåo entre os testes de Mitsuda e interferon-gama; 55,6 por cento de correlaçåo entre os testes in vitro (linfoproliferaçåo e interferon-gama). Quando estes três testes foram considerados em conjunto, uma correlaçåo de 38,9 por cento foi observada. Este estudo demonstra a heterogeneidade do comportamento imunológico mediado por células e anticorpos em pacientes com hanseníase BT, apesar de todos histologicamente serem capazes de conter a multiplicaçåo bacilar e de formar granulomas epitelióides