Pattern of inflammatory response to Loxosceles intermedia venom in distinct mouse strains: A key element to understand skin lesions and dermonecrosis by poisoning

• The venom show hyaluronidase, collagenase, proteolytic and sphingomyelinase activity.
• All mouse strains tested here showed a significant paw edema after venom inoculation.
• C57BL/6 mice have a preferential innate immune response against L. intermedia venom.
• BALB/c mice have a preferential acquired immune response against L. intermedia venom.

Envenomation caused by spiders Loxosceles induce intense dermonecrosis at the bite site and systemic disease. In this work we described the hyaluronidase and collagenase activities in vitro of the Loxosceles intermedia venom, but no phospholipase A2 activity. In vivo, we evaluated the effect of L. intermedia venom used different strain of mice, C57BL/6, BALB/c and Swiss. All mice developed paw edema after venom injection, persistent for 24 h in BALB/c and C57BL/6 mice. Histopathological analysis of the skin after venom injection revealed vascular congestion in Swiss mice and an inflammatory reaction in BALB/c and C57BL/6 mice. The mobilization of inflammatory cells from bone marrow, spleen and blood was investigated. Typical innate immune response with mobilization of myeloid cells and cytotoxic CD8 T lymphocytes was observed in C57BL/6 mice. In contrast, typical acquired/humoral immune response was observed in BALB/c mice, with preferential involvement of conventional B lymphocytes and CD4 T helper cells. The skin inflammation associated to mobilization of inflammatory cells indicated that mice models are strongly recommended to investigate specific cell types involved with immune response to the envenomation and mechanisms to inhibit skin lesions.