Although the story of the African sex workers who seem to be immune to HIV infection has captured the imagination of many researchers, there is another model of natural immunity that needs examination in more detail. Most babies born to HIV-infected mothers also escape infection even after potential intrauterine exposure and, more important, exposure to virus-containing blood and secretions during labor and delivery. Finally, breast-fed infants ingest hundreds of liters of virus-infected breast milk. Many factors such as CD4 cell counts and viral load in the secretions must be considered. One should add that, like the sex worker model, it is a "real"-world situation of viral encounter opening a window to the "in vivo" infection moment. Although interesting, there are, however, several drawbacks to the model; notably, the newborn is immunologically immature compared with later in life. However, their capacity to produce CC cytokines is greater compared with their mothers whether she is HIV infected or not. This is consistent with the expected skewing toward a stronger innate response rather than the adaptive response.
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