Rasiqh Wadud

INTRODUCTION Free haemoglobin is toxic, reacting with essential regulatory molecules like nitric oxide to cause widespread vascular dysfunction and severe renal damage. A primary role of red cells in all vertebrate species is to safely contain haemoglobin in a protected environment, as well as to facilitate the transport of blood gases.1 Not surprisingly, red cells from different species share many features and challenges in common (Table 1). However, there are also some striking differences.

By Rasiqh Wadud 17th-Jun-2020 When majority of the population develop immunity to a disease either naturally or through immunization by vaccination and it indirectly provides protection by inhibiting spread to susceptible individuals in the community, it is known as "herd immunity", "herd protection" or "community immunity". Polio is a prime example, which was once very prevalent in our country but now occurs very rarely because the vaccine helped establish herd immunity.