The biological activity of LPS depends on the chemical structure of its lipid A. Primarily, TLR4 is required for activation of innate immunity upon recognition of LPS of Gram-negative bacteria . The ability of TLR4 / MD-2 system to respond to a distinct lipid A species are clinically important. Pathogenic bacteria may employ LPS with low biological activity of its lipid A to evade proper recognition by the TLR4 /MD-2 complex, dampening the host immune response and increasing the risk of bacterial dissemination. On the other hand, such lipid A would not be able to induce septic shock in susceptible patients, rendering septic complications more manageable. Yet, defining and understanding how even the smallest structural differences between the very similar lipid A species may affect the activation of the immune response may provide the mechanism for the fine tuning of the latter and new insights to immunomodulatory processes. 
A lipid profile should ideally be measured when a person is healthy. In particular, cholesterol can be temporarily low during acute illness, immediately following a heart attack , or during stress (like from surgery or an accident). To get a true representation of your cholesterol, you should wait at least six weeks after any illness before having it measured. In women, cholesterol and triglyceride conccentrations are high during pregnancy. Women should wait at least six weeks after the baby is born to have a lipid profile measured. Some drugs are known to affect the lipid profile, including oral corticosteroids, beta blockers, oral contraceptives, thiazide diuretics, oral retinoids and phenytoin.