Figure 1

Relationships between cellular and humoral immune responses specific to Mycobacterium avium spp. paratuberculosis (MAP) and MAP shedding. From the basics of immunology we expect that presence of bacteria will stimulate MAP-specific immune responses. While MAP-specific immune responses are expected to impact bacterial replication, whether these immune responses reduce or enhance shedding is not well understood. It is believed that cellular (Th1) immune response suppresses bacterial replication, while humoral (Th2) immune response enhances bacterial replication. Furthermore, the relationship between cellular and humoral immunity (co-expression or cross-suppression) remains incompletely defined although it is generally thought that the two responses are cross-inhibitory [13].