In Ayurveda, body fluid is rasa dhaatu, rakta dhaatu, lasikaa, and so on. Rakta dhaatu is compared with blood, lasikaa is compared with lymph. According to Ayurveda Rasa dhatu is the 1st dhatu which is made of aahara rasa. Rakta dhaatu is the 2nd dhatu which is develops from Rasa dhatu by the action of respective dhaatwaagni. This process is explained by Ksheerdadhi nyaaya, Kedaarekulya nyaaya and Khalekapot nyaaya.
Also it is doubtful if lasikaa can be interpreted as lymph. This is because wide range of functions of lymph is not hidden. Ayurveda in those days was quite advanced medical science. It seems impossible that compendia would not mention a word directly or indirectly about functions of lasikaa. Somehow references mentioned above do not include clues regarding such wide range of functions. Hence, it will not be wise to interpret lasikaa as lymph.