In order to include ITs in a breeding plan to improve pig immunocompetence, the genetic and phenotypic parameters of the different ITs need first to be estimated. Several studies in swine, mice, poultry and cattle demonstrated the possibility of selecting animals with high or low immune response (IR) as characterized by one or a few ITs [2, 7, 8, 9, 10] . A study on Yorkshire pigs selected for eight generations for high and low adaptive IR (HIR and LIR, respectively) on an index combining four standardized measures of specific antibodies and cellmediated IR, after stimulation with specific antigens (bacillus Calmette-Guérin and hen egg white lysozyme), has revealed that HIR and LIR animals differ in response to immunization and infection [2, 11, 12, 13, 14] . Other studies have also shown that various innate and adaptive ITs are genetically controlled. For example, variation in innate ITs, such as NK cells, monocytes, interferon a (IFNa) production or phagocytosis [15, 16, 17] is heritable and several adaptive ITs have moderate to high heritability values including total white blood cells (WBC), CD4 + T lymphocyte, CD8a + T lymphocyte and B lymphocyte subsets [15, 16, 17] , delayed-type hypersensitivity reaction [15, 18] , lymphocyte proliferative response [15] , interleukin-2 (IL2) production by lymphocytes [15] and antibody response [12, 15, 18, 19] . Clapperton and colleagues have also reported that variation in acute phase protein levels is heritable [16, 17] . Finally, several significant QTLs for total leukocyte count ( [20, 21] ; Animal-QTLdb, http://www.animalgenome.org/cgi-bin/QTLdb/index), mitogen-induced proliferation [20] , antibody response [20, 22] , cytokine production (IL10 and IFNc) [23] , complement activity [22] , and acute phase protein serum concentration [22] have been detected and mapped to different pig chromosomes. Taken together these data demonstrate that variation in some ITs is under genetic control. However, most of the results reported so far have targeted a limited number of traits and very few studies have combined innate and adaptive ITs.