Effect of in vivo depletion of PMN leukocytes in mice resistant to and susceptible to pulmonary Paracoccidioidomycosis

Author(s)

Adriana Pina

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2002-04-05

Examining board members

Vera Lucia Garcia Calich; Sandro Rogerio de Almeida; Marcelo de Franco

• Advisor: Vera Lucia Garcia Calich

Abstract

Previous studies in our laboratory defined susceptible (B10.A) and resistant (A/J) mice to pulmonary P.brasiliensis infection. To investigate the role of PMN cells in pulmonary PCM, resistant and susceptible mice were depleted in vivo of these cells by intraperitoneal (i.p.) injection of a granulocyte-depleting monoclonal antibody and infected intratracheally (i.t) with one million yeast cells. Control mice received equivalent doses of normal rat IgG. PMN depletion decreased survival times of B10.A, but not of A/J infected mice. When compared with the non-depleted counterparts, resistant mice presented increased fungal loads in the lung only at day 7 after infection. On the contrary, PMN-depleted susceptible mice presented higher number of yeast cells in the lung, liver and spleen at days 7, 15, 30 and 120 after infection than their IgG-treated controls. PMN cells depletion, however, did not alter the DTH reaction developed by both mouse strains. Regarding humoral immune response, PMN cells depletion caused increased production of specific antibodies in B10.A (Total Ig, IgG1, IgA and IgG3) and A/J (Total Ig, IgG2a, IgG2b and IgG3) mice. Levels of pulmonary cytokines were also altered after PMN depletion. B10.A-treated mice presented increased levels of IL-12 and IL-4 at days 15 and 120 post-infection, respective/y. In A/J-depleted mice, augmented levels of IL-12 were detected at days 7 and 120 after infection; IFN-γ, however, was produced in higher levels during whole course of infection. Thus, PMN depletion induces higher levels of specific antibodies and enhanced pro-inflammatory milieu at the site of infection. As a whole, our data on PMN depletion at the onset of infection showed that neutrophils are important cells in host defense to P.brasiliensis infection. However, the effect of PMN depletion depends on the genetic background of the host and has a more pronounced effect in the susceptible strain of mice. We have also assessed the effect of in vivo depletion of the leukocytes on the acquired phase of immunity developed by B10.A mice previously immunized by the subcutaneous (s.c.) route were depleted or not of PMN cells and challenged i.t. with one million yeast cells. No differences were detected in the CFU counts in the lung, liver and spleen between untreated and PMN depleted vaccinated mice. PMN depletion also did not alter the production of specific antibodies but enhanced IL-3 synthesis as well as DTH reactivity. In conclusion, our results showed that, differently from natural immunity, PMN cells do not play a protective role in the acquired phase of immune response to P.brasiliensis infection. (AU)