Hi, the increased cytokines in serum and brain be because of increased released of monocytes and neutrophils.

Is there a reason why you would not expect to see this? What dose of LPS are you using? A single IP injection with LPS causes septic shock in mice and it is normal to see cytokines go up esp. innate cytokines like IL-6, TNF and IL-1b. When using a single injection of 20-50 mg/kg of LPS, you see strong cytokine responses within 6 hours and you have a lot of mortality. With lower doses, you may have more survival but you could expect to still see an increase in pro-inflammatory cytokines.

LPS activates immune system. wide variety of inflammatory mediators are released which appear to contribute to these responses. These include the release of proinflammatory cytokines ( tumor necrosis factor-alpha, IL-1 beta, IL-6, IL-8). Microglia activation. The different immune response to the administration of LPS also depends :

LPS or mouse strain used, site of injection, quantity of LPS applied, time after the challenge mice were 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4825946/

Thanks julie joseph, I used 0.5mg/kg and many articles stated that 24 h post lps administration, the cytokine levels come to basal levels, whereas when I performed, there is still increased pro-inflammatory cytokine levels in blood in comparison to normal group@ Julie Joseph

There could be many explanations for why your results are different.

Mouse model: Strain, age and gender. Even the same strain sourced from two different suppliers could behave differently. The metabolic status of the mice also plays a role in immune activation.

LPS: Purity and supplier. We used to see differences in immune responses when using ultrapure LPS vs. TCA purified LPS vs. phenol/chloroform extracted LPS. Like before, there could be differences between LPS sourced from different manufacturers.

Storage and dilution of LPS: How is LPS stored, reconstituted and diluted? What buffer did you use for dilution?

Assay: See if your assay is more sensitive than what has been used by others. It could be that the assays that were used were not picking up minor differences.

Check whether there are any differences between your experimental model/setup and the others reported in literature. If you really need to replicate the results, try using the exact same experimental setup.

@ Joaquim Pombo for suggesting a very lucid and clear review article for my query