Determination of HLA antigens has an extensive application in paternity,
   Histocompatibility testing, and disease suseptibility identification. A vast
   arrey of different HLA antisera are required for HLA typing. Such antisera can
   be obtained from pregnant women, transfused patients, immunized animals
   or  hybridoma cells, but still the sera of pregnant women is one of the best
   sources for producing of HLA antisera. The pregnant women usually form
   antibodies to the foreign HLA antigens of the fetus inherited from the father. 
   Due to the genetic variations among different races and the very high price
   of these antibodies it is preferable to obtain these antisera from locally
   pregnant women.

          In this study, sera of 40 primiparous and 65 multiparous pregnant Iranian
   women were screened monthly (for 3 times) againest their husband’s pure
   lymphocytes, using the microlymphocytotoxicity method of NIH.

          Among the primiparous 2 cases (5%) and among the multiparous
   women 9 cases (13.8%) had HLA antibodies in their sera. The titer and score
   of antibody were determined monthly in positive samples. The antibodies
   had the highest level in the 6th month of pregnancy.

          We concluded that the best source and the time to obtain HLA antisera
   are multiparous women in the 6^th month of pregnancy