Receptores tipo toll

Papel de los receptores tipo toll en la inmunidad innata y su implicación en medicina veterinaria Role of toll-like receptors in innate immunity and their implication in veterinary medicine
Carlos Ramón Bautista Garfias* Juan Joel Mosqueda Gualito*

Abstract
The innate immunity concept has undergone a noticeable change during the last five years, due to the discovery of the mammalian Toll-likereceptors (TLRs, transmembrane proteins expressed by cells of the innate immune system) and its role in recognizing microbial pathogens. At present, the study of these receptors is of great interest —mainly in human medicine and recently in veterinary medicine— due to the fact that these have a central role in both, triggering innate immunity as well as coordinating innate and adaptive immunity.This review seeks to show the Toll-like receptor’s concept in the immunity processes from the perspective of their importance in veterinary medicine. Key words: TOLL-LIKE RECEPTOR, INNATE IMMUNITY, VETERINARY MEDICINE.

Resumen
El concepto de inmunidad innata ha tenido un cambio notable durante los últimos cinco años, debido al descubrimiento de los receptores tipo Toll (TLR, proteínastransmembranales expresadas por células del sistema inmunitario innato) en los mamíferos y su participación en el reconocimiento de patógenos microbianos. Actualmente el estudio de estos receptores es de gran interés, sobre todo en medicina humana y muy recientemente en medicina veterinaria, debido a que desempeñan un papel central, tanto en el desencadenamiento de la inmunidad innata, como en lacoordinación entre las inmunidades innata y adaptativa. Esta revisión pretende mostrar el concepto del papel de los receptores tipo Toll en los procesos de inmunidad desde la perspectiva de su importancia en medicina veterinaria. Palabras clave: VETERINARIA. RECEPTOR TIPO TOLL, INMUNIDAD INNATA, MEDICINA

Recibido el 14 de octubre de 2004 y aceptado el 7 de abril de 2005. * Centro Nacional deInvestigación Disciplinaria en Parasitología Veterinaria, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, km 11.5, Carretera federal Cuernavaca-Cuautla, 62550, Jiutepec, Morelos, México.

Vet. Méx., 36 (4) 2005

453

Introduction
volution has armed mammals with two main forms of defense against infectious agents: innate immunity and adaptive immunity. The first one provides ahost defense against invading microbes which is immediate, unspecific and which does not have memory, while the second one is naïve, gradual and must be taught through somatic generation of a diverse receptor repertoire, in order to develop an appropriate immune response against invading agents.1 This difference in reaction suggest that all innate immunity responses must be based on the recognitionof molecular patterns associated to microorganisms. In contrast, the adaptive immune response depends mainly in two types of specialized lymphocytes, T lymphocytes and B lymphocytes, which specific receptors are generated somatically in response to antigen presentation by professional antigen presenting cells (interdigitant dendritic cells, macrophages and B cells). 2 This process induces anantigen-dependent clonal expansion of lymphocytes T and B, which gives as a result, long lasting humoral and cellular immune responses. However, acquired immunity does not occur immediately in response to a new antigen or pathogen and the delay in the response could have a devastating effect on host survival. 3 Therefore, the innate and the acquired immune responses are coordinated in such a way thatthe innate immune response represents the initial process which directs the defense of the mammal host. 3 Microorganisms express molecular patterns which are specific and easily differentiable from those of the host; these include double stranded viral RNA; unmetylated CpG dinucleotides present in bacterial DNA, but scarce in vertebrates; manans from yeast; mycobacterial glicolipids; lipoproteins...