Is there a relation between polyclonal spike n increased plasma cells in the bone marrow pls answer?

Short answer is yes: Reactive, meaning not malignant, causes of plama cell increase in bone marrow is not uncommon. In the setting of reactive processes such as inflammation, infection, cirrhosis, immune mediated anemias one can see an associated polyclonal increase in globulins (although I would not call that a spike).

Relevance?: is there any relevance to any illness? Whenever there is polyclonal spike in the activity of the bone marrow, all cell types may increase in number. Plasma cells are related with B lymphocytes with more complex origination and maturation pattern involving lymphoreticular system.