It would appear that you have these tables and relationships:
Antibodies-----<antibody occurrence>-----Antibody Identification
Antibodies::__pkAntibodyID = antibody occurrence::_fkAntibodyID
Antibody Identification::__pkSpecimenID = antibody occurrence::_fkSpecimenID
You can place a portal to antibody occurrence on the Antibodies layout to list and select Antibody Identification records for each given Antibodies record. Fields from Antibody Identification--such as the Significance field, can be included in the Portal to show additional info about each selected Antibody Identification record and the _fkSpecimenID field can be set up with a value list for selecting Antibody Identification records by their ID field.